Tyre Pressure

declan1

I've always been riding 25mm tyres at around 110psi. Seems a good standard for me (68KG).

I got some Vittoria Zaffiros the other day (25mm), and pumped them up to 110psi as normal (130psi is max rated).

When climbing out of the saddle, the front tyre 'rolls' either side of the rim as if it's flat. It doesn't look right - I tried 130psi today and it was a bit better, but not much and it was really uncomfortable!

So... is the side-to-side rolling normal?

Thanks!

wellbeloved747

Because the tyre is 2mm wider there is a larger volume to fill with air. you can counter act this effect by putting huge pressure in the tyre however it will tear. i only tend to use 25mm for the winter as they flatten out more like an mtb tyre and give better grip. if not just stick to 23mm if you don't like the feeling.

declan1

wellbeloved747 wrote:

Because the tyre is 2mm wider there is a larger volume to fill with air. you can counter act this effect by putting huge pressure in the tyre however it will tear. i only tend to use 25mm for the winter as they flatten out more like an mtb tyre and give better grip. if not just stick to 23mm if you don't like the feeling.

The thing is my old tyres were also 25mm, however they didn't do the sideways rolling like the Zaffiros?

wellbeloved747

oh i thought you said you rode 23mm my apology. my only guess is that the wall of the tyre is thinner than what you are use to and doesn't support the tyre as well. did you change the tube?

declan1

wellbeloved747 wrote:

oh i thought you said you rode 23mm my apology. my only guess is that the wall of the tyre is thinner than what you are use to and doesn't support the tyre as well. did you change the tube?

Yeah I got some new Schwalbe tubes, which if anything are thicker than my previous ones. I think it's maybe the sidewall as you said

stueyboy

I just got some of the 23mm Zaffiro's (maybe due to the same thread you might have read?) and the sidewalls do look thinner than the middle so maybe that is affecting the feel you are getting.
Not to say they are thinner than normal but the middle is definitely thicker than what I had before. I pumped mine up to 100 front and 110 rear and they rode quite well and weren't any slower despite being a bit heavier.

declan1

Sorry to bump this thread, but can anyone else help with this?

Thanks!

goonz

Maybe its just the extra weight causing it to do that and the thinner side walls?

declan1

There isn't any extra weight. I'm beginning to think it's the sidewalls. Surely they would make them stronger? I'm only 68KG so not exactly a lot of excess weight.

goonz

I meant when you stand on the bike whilst climbing...but most likely the sidewalls...

declan1

My old tyres, cheap chinese 25mm CST things, wouldn't do it. They stayed solid and didn't roll side-to-side.

This is really annoying me now - I'm gonna have to wait until these wear out to get some different ones!

declan1

Ok, little update - I've tried my old 25mm CST tyres again, and noticed they also roll side to side. My 23mm CST tyres do this as well. It's really annoying me now.

Does anyone else have this problem? If it's normal then it probably won't bother me as much but I expect them to be pretty solid when climbing out of the saddle.

TOM14S

Just buy Michelin... Problems solved

Turbokid

Is your pump gauge knackered?

cougie

Is it in your mind rather than in real life ?

imposter2.0

declan1 wrote:

Does anyone else have this problem? If it's normal then it probably won't bother me as much but I expect them to be pretty solid when climbing out of the saddle.

flexible rubber casing, held up by nothing more than air pressure - why do you expect it to be 'solid' ??

keef66

I ride 25mm GP 4 Seasons and have them at 70 front and 80 rear which I find gives a comfortable ride, but I have to be on the lookout for potholes because those pressures offer little protection against pinch flats. My front tyre squirms a bit when I'm stomping up short, sharp hills, but a 25mm tyre at 110 psi I would expect to be rock solid.

deswahriff

...I'm about the same weight as you, 67kg and run Michelin 25mms at 90psi...never noticed anything like you describe....

declan1

Sorry to keep bumping this thread up but I'm getting seriously annoyed by this now. I've just tried three different tyres (two 25mm and one 23mm) and three different tubes but they ALL look flat when I'm standing out of the saddle.

I've not noticed this before and my dad's Giant PR-2 tyres don't do it at all.

Please help!

imposter2.0

would it help if I said "it doesn't matter - stop worrying about it" ?? Or if it still bothers you - buy some Giant PR-2 tyres.

ManOfKent

Have you checked your pump, as suggested by Turbokid? Maybe the tyres aren't pumped up to the pressure you think.

Otherwise, follow Imposter's advice, or just stop looking at the tyres and start looking at the road ahead.

declan1

ManOfKent wrote:

Have you checked your pump, as suggested by Turbokid? Maybe the tyres aren't pumped up to the pressure you think.

Otherwise, follow Imposter's advice, or just stop looking at the tyres and start looking at the road ahead.

I'll try and compare it to a different pump tomorrow, but when I pump the Giant's tyres up to 120psi with my pump they don't look flat whatsoever :?

Cheshire Cat

I run Schwalbe ZX DD in a 25c at 90psi front and rear and have never noticed this and I weigh 82kg - I live in the Lakes, where getting out of the saddle to finish off a climb is considered the norm. What rim are you using, if the rim is too narrow (19mm) the tyre will bulge, potentially causing the tyre to roll on the rim.

declan1

Cheshire Cat wrote:

I run Schwalbe ZX DD in a 25c at 90psi front and rear and have never noticed this and I weigh 82kg - I live in the Lakes, where getting out of the saddle to finish off a climb is considered the norm. What rim are you using, if the rim is too narrow (19mm) the tyre will bulge, potentially causing the tyre to roll on the rim.

They're Mavic MA-2 rims. I have no idea what width they are but considering they're probably about 20 years old I would think they're quite narrow. My dad's ordered some Continental GP4000s so I'll see if I can try his tyres and see what they're like