Help with tyre pressure

[marko]

I am new to all of this so please be gentle with me.

So I am 40 year old, 18 stone and only 5'11" and realising that I am looking at an early grave have taken the decision to do something about it.

So through my employers cycle to work scheme I have invested in a Trek 7300 bike which seems to fit me just nice.

But I am having an issue with tyre pressures.

The tyres are Bontrager Galaxy 700x35c puncture resistant and are marked with a maximum pressure of 90psi.

The problem is that at 90psi, with my slightly large behind on the seat, the tyres are looking rather sad and out of shape and there is a lot of noise and drag from them.

If I inflate to 110psi, all is good but of course I am 20psi what the tyre wall states.

So what to do.

Run under inflated? To my thinking this would just make the ride harder work and also lead to premature wear.

Run over inflated as I am (but at what cost)?

Of course there is also the question. Is this right?

Any advice is welcome here because as I said, I am just starting out and at 14 days in at 5 miles per day I recognise I have a long way to go.

Thanks

 

[Banjo]

Hi there welcome to the forum.i started 6 months ago similar situation to yourself,have lost over 2 stone from 16 at the start.

Im surprised that your tyre seems to bulge a lot at 90 psi Even at 18 stone.Have U double checked the gauge you are using?Maybe your bike shop could check pressures for u as a comparison.

I have heard people say that an extra 10 lb over the max is ok but as a beginner myself dont know if thats good advise or not.

Good luck with the cycling and the weight losing.

 

[MacB]

Mark, I don't know the answer but have had both ends of the spectrum advised. I use 35mm M+ tyres for my commuting, I was 18 stone, never had a puncture:-

at start I ran them at 55 psi, so lower end of suggested range, as recommended by mechanic for comfort. Did have issues with spokes on rear wheel.

now run them at 85 psi, but different rims, don't notice any comfort difference but they go a bit faster and I am a lot lighter

 

[marinyork]

110psi sounds too high for a 35C tyre. If you're unhappy with the tyre and want to get a higher pressure with less drag I suggest you think about getting some 700x28s on that can take the sort of pressure you want, not right away of course, after a while.

 

[Paulus]

Keep them at the maximum pressure stated on the tyre wall. You will get a bit of noise and drag from them as they are quite a large tyre, but as you weight comes down as you hope, things will get easier and then maybe go down to 28's, they will be faster as they have less rolling resistance.

 

[byegad]

I've read that 1 bar, 14psi over sidewall spec' is probably OK. TBH I'd probably ride at no more than 7psi over max myself! BUT a 35mm tyre with 90psi in it should be ok for 18 stone. I started at 16 1/2 stone with 35s and at 90 they were not challenged at all.

I suspect it's the gauge reading too high. As a previous poster says get the pressure checked by an LBS.

 

[VictorL]

Just wanted to say good luck with the weight loss. i was 18st 10lbs not so long ago (6ft tall). Am now just under 14stone.

Get into the habit of eating sensibly and exercising, and it is relatively easy.

 

[SimonRoberts0204]

18 stone is 252 pounds, so each tyre (assuming symmetry) is supporting 126 pounds.

Therefore, at 90psi , each tyre will have a contact surface on the road of about 1.3 square inches (a little less, allowing for tyre rigidity).

Doesnt sound like much when you think of it like that....

 

[marko]

Thanks guys

I have had the gauge checked and now have a new pump with a gauge that actually displays the correct pressure.

I knew something had to be wrong somewhere.

Cheers