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Author Topic: Tire pressures and handling  (Read 1661 times)

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General_Apathy

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on: August 07, 2018, 03:05:41 pm
I am finding the front end very twitchy on my bike. It seems to be overly effected by changes in road surface and particularly by small ruts. My first thought is the tire pressures which seem to be very low in the manual for the front tyre (20). I have upped it to 22 tonight which felt slightly better but still the front isn't very confidence inspiring. I am sure others have experimented and I would be interested to know their conclusions. I am 6 foot and 12 stone for reference. One other thing I noticed was that I am able to turn the rear Springs round by hand very easily, is this normal? Surely it should be under some load?


Richard230

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Reply #1 on: August 07, 2018, 04:57:33 pm
Instead of relying on the owner's manual for the recommended air pressures, look for them on your VIN/information sticker which on my B5 is on the down-tube. For my Bullet's skinny tires the specified tire pressure is 24 psi, front and 32 psi rear.
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Paul_42

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Reply #2 on: August 07, 2018, 06:36:18 pm
Hi mate, I'm running 30psi at the front and 32psi on the rear. I had same issues when I first got mine. It would lose the front end forcing me to stand it up mid corners. Check your front tyre for scalloping( humps and bumps). I raised my front forks about 8mm so the the tops are sticking out of top clamp. If you can turn the rear nut on the shock then it's not set up. My rears are turned in about 7 thread counts. I've also gone up a profile front and rear so I can flick the bike in and out of twisty's faster. Also change fork oil. I went 10 weight and it's been great. Other more experienced gents will chime in but the above set up works for me. I'm about 98kg wet to give you an idea.
Cheers
Paul.


General_Apathy

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Reply #3 on: August 08, 2018, 02:13:53 am
Thanks fellas. The official figure is definately 20 for the front which feels dangerous to me. Not sure if it's intended for lighter people or maybe Indian roads? @Paul_42 - Glad it's not just me, I have lost the front end twice now. First time I put it down to the smooth tar on the road second time no explanation. I will keep upping the pressures to find my sweet spot.i will be swapping out the fork oil as well at some point. Regarding the rear springs, I am able to turn the actual Spring round by hand on both sides. Usually the spring is under pressure so I am wondering if this is an Enfield thing or my shocks aren't set up right.


gizzo

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Reply #4 on: August 08, 2018, 07:38:48 am
I'm with Paul. usually around 30/32, a bit lower at the track. It definitely feels sketchy when the front is down around 24. Would you let us know how you get on after you've tried them pumped up? I can't think of any time I've felt my bike tramline or the front slide, apart from a brand new tyre incident and once or twice at the track, fooling around with pressures. What tyres you have on?
I think you're right about Indian figure vs the Real World. They'd be looking for a comfortable ride as they thud along looking for MPG's. Cornering ability would have very little meaning to them.
I can turn my springs by hand too, when the bike's on the centre stand. I haven't as much preload as Paul, 68kg here.
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Donat Santowiak

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Reply #5 on: August 08, 2018, 04:29:51 pm
Not sure if I understand the physics of how the front end works but........ The tyre pressure would affect the tyre flex, like speed and forces in compressing/rebounding of the carcass. Would that not affect the performance of the spring rate and the volume/viscosity of the dampning oil? (And valving). So are the forks be factory matched to a 20psi tyre pressure? Hence not really coping with 30psi.
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Paul_42

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Reply #6 on: August 08, 2018, 06:48:55 pm
Well, yeh. We aren't Indian roads or speed limits. Try what myself and gizzo said. Personally with my fat bones the 30/32 psi seems to be the sweet spot. Set the sag. I've given you my settings as a base point to start off with. As you, I had major issues with the front wanting to wash out and having to stand it up mid corner Which getting rid of the sports demons fixed half the problem. Other half was raising front forks and changing fork oil. (Almost 100ml difference between forks). I love the twisty stuff and with the old girl behaving I'm finding I'm backing off from the bigger bikes because it's so much more stable and quicker in the turns. Hope this helps a bit mate.
Paul.


General_Apathy

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Reply #7 on: August 09, 2018, 02:14:14 am
Thanks again Paul and Gizzo. I will update on changes to feel as I tweak the pressures. Which tyres did you swap to Paul?
@ Donat - I am not sure that the tyre pressure vs fork oil/Spring works that way, certainly not at this level of fork sophistication. All I can go on is seat of the pants feel and at 20 psi, at my weight and riding style the front feels very loose.
Have to say it has been a long time that I have been this hands on with a new bike, bloody loving it!
« Last Edit: August 09, 2018, 02:16:45 am by General_Apathy »


Donat Santowiak

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Reply #8 on: August 09, 2018, 02:40:08 am
Thank you everyone for sharing your experiences regading this topic. Although I wonder if RE India had set front tyre pressure to a low 20psi because of poor road surfaces. Why don't  they recomend 20psi for the rear tyre as well?
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tooseevee

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Reply #9 on: August 09, 2018, 06:55:38 am
Thank you everyone for sharing your experiences regading this topic. Although I wonder if RE India had set front tyre pressure to a low 20psi because of poor road surfaces. Why don't  they recomend 20psi for the rear tyre as well?

            Because the wife, the mother-in-law and the three kids are on the rear tire.
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gizzo

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Reply #10 on: August 09, 2018, 07:16:58 am
Thank you everyone for sharing your experiences regading this topic. Although I wonder if RE India had set front tyre pressure to a low 20psi because of poor road surfaces. Why don't  they recomend 20psi for the rear tyre as well?
Because they don't get performance riding in India? Funny story, I was scolded by an Indian person riding a Bullet in the hills one day. I tore past him, hit the rev limiter a couple times and generally went about my business as is my wont. He caught up at a bike café and tried telling me I shouldn't be riding the Enfield like that. He sure as hell couldn't.
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Guaire

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Reply #11 on: August 09, 2018, 08:05:58 am
Well, yeh. We aren't Indian roads or speed limits. Try what myself and gizzo said. Personally with my fat bones the 30/32 psi seems to be the sweet spot. Set the sag. I've given you my settings as a base point to start off with. As you, I had major issues with the front wanting to wash out and having to stand it up mid corner Which getting rid of the sports demons fixed half the problem. Other half was raising front forks and changing fork oil. (Almost 100ml difference between forks). I love the twisty stuff and with the old girl behaving I'm finding I'm backing off from the bigger bikes because it's so much more stable and quicker in the turns. Hope this helps a bit mate.
Paul.

Paul - If not the Pirelli Sport Demons, what tires are you using?
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Richard230

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Reply #12 on: August 09, 2018, 08:52:18 am
Speaking of tire wiggles, if you ride on grooved pavement with tires that have a radial tread design, you may experience a handlebar wiggle caused by the tread following the grooves in the pavement, which would not be apparently to a car or truck, or motorcycle tires with a different tread design.
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Donat Santowiak

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Reply #13 on: August 09, 2018, 04:13:45 pm
If RE India has designed a machine for such poor road and use/abuse. Why are we trying to turn a draught horse into a pretend race horse?. Why not just buy a performance bike in the first place.
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Arizoni

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Reply #14 on: August 09, 2018, 04:20:53 pm
Tire pressures on the middle sized British motorcycles back in the '50's and early '60's were often as low as 18 psi for the front tire and 24 psi for the rear.
This includes Triumph's, BSA's, Velocette's and Matchless's.

In those days the cross bias, tube tires had very stiff sidewalls which didn't need a lot of air pressure to support the motorcycle.

The Avon Speedmaster tires that come on a lot of the new Royal Enfields are basically the same tires that they were back in the '50's with the same ply construction so they don't need a lot of air pressure to work.  About the only real difference in the Avon tires today is they are using better rubber compounds than they did back "in the days".

I don't know what tires the CGT's come with but if they are the newer style, higher air pressure might be more suitable. 

Jim
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Paul_42

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Reply #15 on: August 09, 2018, 05:21:33 pm
Sorry, arvo shift at the hospital is killing me lately. I'm running Bridgestone BT45's. 130/80/18 rear
110/80/18 fronts. Have not had the front wash out ,the rear will give me a gentlish wiggle when lent over too far with too much throttle but it's a fun sort of wiggle where I usually open the throttle more. Oh. Went taller profile too if you didn't pick that up. Tips in faster 8)


gizzo

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Reply #16 on: August 09, 2018, 05:51:24 pm
If RE India has designed a machine for such poor road and use/abuse. Why are we trying to turn a draught horse into a pretend race horse?. Why not just buy a performance bike in the first place.
RE didn't design the chassis. They farmed it out to Harris Performance. This is a company that  knows how to make good handling bikes. And they bought in suspension from Paoli (OK it's not cutting edge stuff, but better than what the Bullets come with). So with the GT you get an actual good handling motorbike. It's just slow, but that's ok.
FWIW I don't have a problem with the Sport Demons. I have one on the front and a BT45 on the back. 'Cause that's what they had when I needed a tyre.
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ace.cafe

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Reply #17 on: August 09, 2018, 09:15:07 pm
IMO, they just reprinted the C5 manuals for the most part.

Again, IMO, this all stems from the original early C5 bikes which had flawed handling due to poor geometry in frame/suspension. The bikes were very twitchy at speed, speed wobbles, etc. Well documented.  The "fix" was to use a low pressure in the front to slow down the response of the front end by a underinflated front tire. Later models has changes to fork and front wheel to correct the matter, but the manual was never corrected. They never admitted that there was any "design error" probably to avoid the cost of a recall.

So, to this day, you see the low pressure spec in the manual.

Sad.

I have been recommending 28/32 for years, and still stand by it.


Donat Santowiak

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Reply #18 on: August 10, 2018, 04:40:40 am
Would be interesting to learn from Pirelli on what optimum pressures/rim width/bike +rider weight the Demons are designed for.
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Guaire

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Reply #19 on: August 10, 2018, 07:56:02 am
Would be interesting to learn from Pirelli on what optimum pressures/rim width/bike +rider weight the Demons are designed for.

I trust the feedback from the experienced riders here more than anyone. I don’t think Pirelli has test drivers experimenting with tires on their own Continental GT.
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Richard230

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Reply #20 on: August 10, 2018, 08:13:22 am
Would be interesting to learn from Pirelli on what optimum pressures/rim width/bike +rider weight the Demons are designed for.

I have been reading tire manufacturer "fitment guides" for years. They list most motorcycles and the tires that they sell that will fit that brand, model and year. They also include recommended tire pressures and would usually provide a pressure for the front and rear tires when riding solo and when fully loaded. Very useful.  Then a few years ago the tire companies, in their customer fitment brochures, stopped providing the solo riding pressure information and are now showing only the maximum tire pressure recommended for each motorcycle. More often than not these pressures tend to be 36 psi front and 42 psi rear.

I am looking at my 2013 Dunlop tire fitment catalog, which has a section covering Royal Enfield models, but not the GT. All of the traditional models are listed, from 1996 through 2012, and all use the same tire, the K70, with a recommended pressure of 24 psi in the front and a 32 psi in the rear tire.  My 2013 Michelin tire guide lists their tires that would fit a lot of strange motorcycles and scooters, but Royal Enfield is not one of them. So I recommend that you visit the various tire manufacturer web sites and get the latest information on tire availability and pressure recommendations from that source.
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portisheadric

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Reply #21 on: August 10, 2018, 12:17:08 pm
Avon SM MKII come in at 24 and 29 for the 325x19 and 350x19.
Nothing listed on their site for the 535GT :(

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General_Apathy

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Reply #22 on: August 12, 2018, 04:56:07 am
If RE India has designed a machine for such poor road and use/abuse. Why are we trying to turn a draught horse into a pretend race horse?. Why not just buy a performance bike in the first place.
For me that is the charm of the bike. I have had plenty of very fast bikes and they leave me cold. Clinically efficient with easy speed albeit at mph way beyond what is allowed. The GT operates at a speed that matches the roads I ride. As I understand it's been developed to handle but the front feels all wrong when you are pressing on. I already had my doubts about the tyre pressures and these guys have answered my question from experience and that's good enough for me. This bike will be a work in progress, it will grow with me and that's it's appeal :)


ace.cafe

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Reply #23 on: August 12, 2018, 08:38:07 am
For me that is the charm of the bike. I have had plenty of very fast bikes and they leave me cold. Clinically efficient with easy speed albeit at mph way beyond what is allowed. The GT operates at a speed that matches the roads I ride. As I understand it's been developed to handle but the front feels all wrong when you are pressing on. I already had my doubts about the tyre pressures and these guys have answered my question from experience and that's good enough for me. This bike will be a work in progress, it will grow with me and that's it's appeal :)

Our CGT riders who have been road testing our billet head prototypes have easily exceeded 100 mph on the factory bike with more appropriate pressures.


Donat Santowiak

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Reply #24 on: August 12, 2018, 04:16:14 pm
With no formal mechanical or motor engineering qualifications my views on how things work on motorcycles are either seat of the pants or self concluded. And hence may be way off the real science of what actually happens. Given all this, if my bicycle tyres run on 60psi ther ride is tolerable but at 100psi it jumps around like a wild bronco. This is because it has no springs or dampening. So how can a 30psi tyre pressure on my CGT not affect the suspension who's job it is to manage the extra forces. Given that apparently it is designed to work at 20psi (30% less). I rest my case.
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General_Apathy

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Reply #25 on: August 12, 2018, 04:53:23 pm
With no formal mechanical or motor engineering qualifications my views on how things work on motorcycles are either seat of the pants or self concluded. And hence may be way off the real science of what actually happens. Given all this, if my bicycle tyres run on 60psi ther ride is tolerable but at 100psi it jumps around like a wild bronco. This is because it has no springs or dampening. So how can a 30psi tyre pressure on my CGT not affect the suspension who's job it is to manage the extra forces. Given that apparently it is designed to work at 20psi (30% less). I rest my case.
So are you running 20 front and 30 rear as per the manual then on your GT? How does your bike feel mid corner at speed? Does it feel planted compared to other bikes you have ridden? Wondering if it may be down to riding style maybe? Just to be clear, I am not talking about knee down, pegs scraping speed here. I am talking about out for a ride, flowing bend swinging kind of speed.
« Last Edit: August 12, 2018, 05:02:36 pm by General_Apathy »


Paul_42

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Reply #26 on: August 12, 2018, 05:22:45 pm
With no formal mechanical or motor engineering qualifications my views on how things work on motorcycles are either seat of the pants or self concluded. And hence may be way off the real science of what actually happens. Given all this, if my bicycle tyres run on 60psi ther ride is tolerable but at 100psi it jumps around like a wild bronco. This is because it has no springs or dampening. So how can a 30psi tyre pressure on my CGT not affect the suspension who's job it is to manage the extra forces. Given that apparently it is designed to work at 20psi (30% less). I rest my case.
How does the GT compare to a pushy?? Go off the book then if you are more comfortable to go off information that's designed to cope with 3rd world roads and 10 up on the one machine. As already stated. The book is incorrect and was written to cover up frame shortcomings. There is a wealth of PRACTICAL hands on knowledge. I may have read into your post the wrong way (which i'm hoping i have) .Guys have given first hand experience including myself on setting up the bike to getting it to handle around bends.( Fark, i better not mention ive inverted my rear shocks then. There will be an Indian exorcist knocking at my door) If your not willing to take on board the R&D that's been done real time on real roads by real owners that love our bikes to death then follow the book, stay at your 20 psi and please dont whine about the bike wanting to throw you off mid corner.
Heres a snip from Putty road with the mods apart from fork oil replacement. Running 32/30 chasing down (trying to) a mate on his firestorm.
https://www.youtube.com/watch?v=PtNaqhQHKYc&t=388s


gizzo

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Reply #27 on: August 12, 2018, 06:56:38 pm
First off, the suspension wasn't designed to work with a 20psi tyre.  It was designed to cope with a variety of surfaces with a reasonably diverse range of loads on it.  It's not a clever fork. It just gets the job done.  Even if it were made for a 20psi front, once you went to a different tyre, you're out of spec again, because all the tyre carcasses are not the same.
Second,  what Paul said. ^
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gizzo

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Reply #28 on: August 12, 2018, 07:05:12 pm
Nice ride, Paul. I was under the impression the Nasho is cop and motor home infested. Looks OK on that day 😎
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Paul_42

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Reply #29 on: August 13, 2018, 08:13:05 am
Hi mate. That one was Putty rd chasing stevevtec. 8)


gizzo

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Reply #30 on: August 13, 2018, 10:19:14 am
Ah.  Looks like CSS worked it's magic on his riding. Looking good.
simon from south Australia
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Paul_42

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Reply #31 on: August 13, 2018, 05:19:51 pm
Yeh it did. His ridings pretty dam good. Been out a few times follwing him and picked up some pretty good tips along the way. Top bloke that one.


gizzo

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Reply #32 on: August 13, 2018, 08:10:07 pm
He is a good egg.
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Greg

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Reply #33 on: August 19, 2018, 10:04:02 pm
Been horsing around with tire pressures since I bought the bike. I'm 145 lbs, ride on fairly smooth roads and find that rear 30-32 with 24-25 front seems to be optimum for me. 20 on the front has just never felt right.


KD5ITM

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Reply #34 on: September 16, 2018, 04:02:17 pm
I run about 26 PSI both front and rear. Works just fine.
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Reply #35 on: September 23, 2018, 03:54:40 am
Changed from the Pirelli Demons to Avon  AM26 - posted about them in another thread

I never felt that the Demons were suited to the Continental.

For riding around town on the AM26 it  feel like a different bike, much better - none of that horrible tramlining - yippeeeee!

Early days, but they seem to offer more feedback on the twisty backroads than the Demons for me


General_Apathy

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Reply #36 on: September 25, 2018, 06:31:48 pm
Well after a little bit of trail and error ended up at 28 Front and 30 Rear and the bike feels stable and confident to turn. 20 is definitely off IMHO and borderline dangerous. Thanks for all the feedback, much appreciated.