A forum for owners of Yamaha TTR250 trail and enduro bikes!

burton500 · Veteran Member

Tyre pressures

Cubber · Super Guru

How High is a Chinaman? aww confuse

The ever posed question is hard to answer because so much is based on personal satisfaction.

Pressures can vary on circumstances:-

Your weight, bike's weight, tyre sizes and makes, terrain and going, weather and temperature, etc., etc.

Start off with a test basis of say 20 psi in front and rear.

Settle the front pressure first by riding on the chosen surface and noting if the wheel bounces or deflects.

If it's very bouncy and choppy it indicates too high a pressure so let some air out.

If it feels squashy and vague then put a bit more air in.

When the front is to your liking move to adjusting the rear. Same applies regarding bouncing or vagueness. Adjust accordingly.

After a few rides you may fine tune to your satisfaction. smile

My TTR is used on tarmac and trail. Front Michelin Comp IV is 16 psi. Rear Pirelli MT43 is 14 psi. These suit me but may not suit everyone.

Good luck.

Martyn

BM Steve · Guru

That is a difficult question, I run Dunlop 606's,they have very heavy side walls and are fitted with extra heavy tubes

I ride in rocky terrain and run 12psi minimum

First off though, get yourself a good tire pressure gauge and use it all the time, keep it on the bike easy to get to, don't trust the ones in service stations, they are rarely accurate

also is the terrain you ride in , rocky, smooth, sandy ??

Start at 12 and adjust up and down use more in rocky of course !

Don't go below 8psi, you might get a pinch flat or spin the tire on the rim

Also your weight and how much you carry on the bike will effect the tyre pressure as well

Obviously, more weight = more air pressure

Cheers

BMSteve

dlowenst · Member

I ride my TTR exclusively off-road, and run between 12 and 14 psi front & back, depending upon the terrain.

Dave

TTRfan · Super Guru

A word of warning to users of UHD inner tubes.

Our local guys have been having trouble with the valves ripping out as the UHD tubes were moving back and forth inside the tyre on each acceleration or deceleration.

A member just bought a new UHD tube for the front of his bike and he did some tests before fitting.

UHD tube; 9psi, tyre not quite filled; 10psi, just filled; 11psi completely filled but not "gripping" the tyre.

Standard Cheng tube; 3psi, filled; 4psi, completely filled and bulging.

The other thing was, inflated outside the tyre, the UHD tube starts bulging unevenly at 9 to 10 psi and the standard tube seemed to inflate more evenly but you can't go beyond about 4psi.

Conclusion, you should run a minimum of around 15psi on a UHD tube as it requires more pressure to fill the tube and stop them moving, a lot more pressure.

Brian

BM Steve · Guru

I had some concern about slipping so fitted 2 agressive rim locks to the back wheel

spaced them and the valve evenly around the rim

elongated the valve hole just in case

bent some heavy duty steel washers around some pipe and put them under the rim locks, tightened them up with some thin rubber sheet under the washers to keep the water out, that helped a lot to tighten them down nice and tight

so far so good, no slips etc

I also balanced the wheel after all that, I used some self adhesive wheel weights, ended up using 200grams to get a balance

PS. maybe my tyre helps as well, I had to get the bike shop to fit the rear tyre

maybe my tubes aren't ultra heavy, they are michelin with 3mm walls

biggrin

TTRfan · Super Guru

You will know if your tube is moving inside the tyre as you will find abrasion marks on the tube and little balls of rubber from the tube in the tyre!

BM Steve · Guru

TTRfan wrote:
You will know if your tube is moving inside the tyre as you will find abrasion marks on the tube and little balls of rubber from the tube in the tyre!

So that's what causes that, my last tube looked like that, I won't be pulling the tyre off to find out on the new one though biggrin I'm not that keen to find out !

TTRfan · Super Guru

BM Steve wrote:
TTRfan wrote:
You will know if your tube is moving inside the tyre as you will find abrasion marks on the tube and little balls of rubber from the tube in the tyre!

So that's what causes that, my last tube looked like that, I won't be pulling the tyre off to find out on the new one though I'm not that keen to find out !

It took me a long time (and a few expensive tubes as you can't repair a ripped out valve cry ) to work out what was happening!

Brian

tracker · Veteran Member

I have mousses (spelling right?) fitted front and rear,they are exspensive, but i have been too many times on a wet welsh mountain repairing tubes.When it is wet,cold,and getting dark the cost is worth it.As for fitting them i can do the front ok,but i use my mates tyre fitting jig that he made from a old car rim,it works a treat.

Gcorner · Veteran Member

We tried smearing lolly water (bourbon and cola) on the beads as we replaced them, haven't torn a valve out since.

brindabella · Senior Member

I think we all agree that when off the main road, we need our pressures as low as possible.
sadly this is constrained by the fact that low pressures can mean pinch flats and tyre creep.

HD tubes were a great advance in reducing the risk of getting a flat tyre.
UHD tubes seem like taking a step too far.
They are expensive and heavy.

If UHD tubes need higher pressure to avoid valve problems, then they are a pointless nuisance.

I reckon that there are two possible causes for these valve problems:

1. the tyre creeps on the rim, especially on the rear, due to driving force and low pressures:

the cure is to have good rim locks (and lolly water?).
enlarging the valve hole in the rim means you can see if creep is happening.

2. each hit on rocks and ledges and potholes deforms the tyre+tube momentarily:

if you have dented a rim you know how much deflection must be happening.
if you have hit a kangaroo and found hair wedged between rim and tyre, you also know.
but even ordinary hits will cause a significant momentary deflection.
if the hit is near the valve position, the valve is also going to move a bit.
after a lot of to and fro valve movement the valve attachment to tube fails.
enlarging the rim hole lets the valve move a bit, reducing distortion at the tube attachment point.
"serious" UHD tubes are too stiff - they transmit deflections into valve movements.

By the way, balancing tyres with rimlocks sure makes a better ride on the street at speed.
But it is hard to find suitable weights.
adhesive lead strips (from a car tyre fitting place) seemed to work reasonably for me.
probably the same ones as BM Steve used.
I clean the rim, hammer them on for good luck, and gaffer tape on top for even more good luck.

burton500 · Veteran Member

Thanks for the tips - I'll start at around the 15psi mark and go from there.

Lee

Haggis Hunter · Veteran Member

brindabella wrote:

if you have hit a kangaroo and found hair wedged between rim and tyre, you also know.

Did hit a chicken once riding past a neighbours house on my way to the garage for an MOT. Well it was more like the chicken crossed the road......at the wrong time!

It got stuck in the front wheel and when it passed through the forks it was good night Vienna. Ended up with feathers stuck to the exhaust which stunk!

Sheep and deer can be a problem at night as well.

I ride over very rocky ground and being a er... stout fellow and as I am often carrying a heavy rucsack I ride with the tyres around 23-25psi front and rear, I have heavy duty tubes fitted and it's rare I get a puncture.

Peter

BM Steve · Guru

some interesting views on UHD tubes on another forum I hang around

OLD BULLS

biggrin