Overweight - Tyre Pressure

RossMu

Sorry, I realise the boards are already overloaded with tyre/p* questions. Over 90% of my p*'s have been on the back tyre. I have done around 2000 miles on the bike, so have some experience at trying to prevent p*'s.:

- Changed for more puncture-proof tyres (SMP/Conti GP's).
- Got into the habit of checking the tyre for left-over debris.

So, 2 questions...

1. Be honest - Weighing just under 200 pounds - I assume from experience this is going to increase the risk of punctures?

2. Can overweight folk safely over-inflate tyres? Currently running the Conti GP at the max recommended 120PSI, but tempted to go higher if it would help.

Thanks,
Ross

letap73

Ross,

Not being too far off 200 pounds myself - I have suffered no punctures on the Bontrager Racelite tyres on my Trek, I have done over 5000 miles on them! They are not the best rolling tyres and I don't have them at the highest pressure most of the time. Obviously having them under pressure increases the chances of a puncture, however, I am certain over inflation does not work either.

team47b

top of this page is about tyre sizes, but the foot of the page is a calculation for total weight to tyre pressure table, shows you how to work out necessary pressures, takes the guesswork out.

http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3802

RossMu

Thanks folks - appreciated!

Hoopdriver

There is little poin in havin your tyres inflated to 120 lbs on the roads. Anything over 110 is actually counterproductive in terms of rolling resistance and will only serve to give you a rough ride and possibly more punctures.

I keep mine at 90-95 rear and 85-90 front. I use Conti 4 Seasons GPS (700x25) and very, very seldom have punctures.

As for your rear tyres accontin fir 90% of your punctures, rear tyres support more of the weight on a bicycle-rider combo an quite naturally puncture more often than the front.

slowondefy2

Hoopdriver wrote:

There is little poin in havin your tyres inflated to 120 lbs on the roads. Anything over 110 is actually counterproductive in terms of rolling resistance and will only serve to give you a rough ride and possibly more punctures.

That all depends on the weight being carried by the tyre and the width of the tyre - your numbers are meaningless on their own. Even the 'small' change between 23 and 25 tyre widths demands very different pressures.

OP, tyre pressures are a minefield, and everyone has an opinion that suits them ;-) I use some of the online calculators to suggest my tyre pressures to get the 'desired' 15% drop, but there's a bit of guess work really. One of these days I'm going to use my scales to work out the fore/rear weight differential between the tyres. I'm not the 'typical Italian cyclist build' like you and I suspect my rear wheel has 65/70% of my weight. FYI, I've not had one puncture through my Gatorskins.

giropaul

I'll ignore the idea that 14 stone odd is overweight - it might be for some, but there are pros who come close. I won races at 15 stone+

Back to tyres - I've never had a problem, even at greater weight now I'm not racing and getting old. 8 bars, and 23's usually, and using mainly Conti 4-Seasons, but also 22mm Veloflex.

Keepng an eye on the road, and going over the tyres for debris after each ride is far more important than how heavy you are.

Headhuunter

Hoopdriver wrote:

There is little poin in havin your tyres inflated to 120 lbs on the roads. Anything over 110 is actually counterproductive in terms of rolling resistance and will only serve to give you a rough ride and possibly more punctures.

I keep mine at 90-95 rear and 85-90 front. I use Conti 4 Seasons GPS (700x25) and very, very seldom have punctures.

As for your rear tyres accontin fir 90% of your punctures, rear tyres support more of the weight on a bicycle-rider combo an quite naturally puncture more often than the front.

That sounds too low to me, certainly 85psi is too low for me... I'm sure I'd be getting snakebites all the time at that pressure and cornering would not be fun. According to the table posted above, at my weight, with 700x23s I should be at least using 120psi. I generally have 120 in the back and 110 in the front and I weight 80kg

bagz3

I'm a tad over 16 stone and i just go with the max on the tyre wall. For me its 115psi and so far so good. As said before, careful riding and checking tyres is key.

Monty Dog

I think the OP should be fitting the widest tyres he can fit - the bigger volume will do more to cushion any impacts than running skinny tyres rock hard. Even Continental's own testing demonstrated that anything over about 7 bar is pointless. If you look on Wiki for 'rolling resistance' you'll find some info that demonstrates why fatter tyres roll faster too.

ddraver

OP - I'm a big boy as well. I run my Conti GP4000S's as such

Rear - 23mm @ 120psi (max)
Front - 25mm @ 100 - 110 for a bit of give

I usually do shorter fast club runs, which usually involve a b it of play racing, If I go out on my own for longer slower stuff, i let a bit out. If you ride crappy roads with pot holes and stuff then this will stop you pinch flatting (unless you properly tw@t them, but then nothing will stop that)

The best tactic though is to experiment, although this can be a bit expensive in tubes if you go too low too often :P

tiredofwhiners

I'm 200 lbs

I never inflate either front of back higher than 105psi, and have not had any particular problems with increased puncture rates. The problem around here (Hampshire) is that the roads are strewn with flint shards half the year which can get through anything eventually. Even when I was 230lbs, I still used 100-105psi without problems, but I check the pressure before every ride, quite religiously.

mouth

I am a porker at 15st+ and have had one p*ncture in around 1500 miles which was caused by a bit of glass. I Keep both front and back somewhere between 90-100psi. I run a Continental somethingorother on the rear and kenda (standard issue on the new bike) front.

alwaystoohot

RossMu wrote:

Sorry, I realise the boards are already overloaded with tyre/p* questions. Over 90% of my p*'s have been on the back tyre. I have done around 2000 miles on the bike, so have some experience at trying to prevent p*'s.:

- Changed for more puncture-proof tyres (SMP/Conti GP's).
- Got into the habit of checking the tyre for left-over debris.

So, 2 questions...

1. Be honest - Weighing just under 200 pounds - I assume from experience this is going to increase the risk of punctures?

2. Can overweight folk safely over-inflate tyres? Currently running the Conti GP at the max recommended 120PSI, but tempted to go higher if it would help.

Thanks,
Ross

Ross I weight 230lbs and run my rear Conti GP's at 110lbs without any problem though don't know why you'd want to go to 120?

slowondefy2

Alwaystoohot wrote:

Ross I weight 230lbs and run my rear Conti GP's at 110lbs without any problem though don't know why you'd want to go to 120?

You can't compare pressures without knowing the tyre widths. Even 23s vs 25s require significantly different pressures.

p9uma

ddraver wrote:

OP - I'm a big boy as well. I run my Conti GP4000S's as such

Rear - 23mm @ 120psi (max)
Front - 25mm @ 100 - 110 for a bit of give

I usually do shorter fast club runs, which usually involve a b it of play racing, If I go out on my own for longer slower stuff, i let a bit out. If you ride crappy roads with pot holes and stuff then this will stop you pinch flatting (unless you properly tw@t them, but then nothing will stop that)

The best tactic though is to experiment, although this can be a bit expensive in tubes if you go too low too often :P

What is the benefit of using different size tyres?

Hoopdriver

Sometimes its useful to have wider tyres in the rear, where the bicycle is carrying more of its weight burden. I never heard of anyone using wider tyres in the front....

slowondefy2

Hoopdriver wrote:

Sometimes its useful to have wider tyres in the rear, where the bicycle is carrying more of its weight burden. I never heard of anyone using wider tyres in the front....

In the thread "23mm to 25mm ????" (in 'Road Buying Advice') someone posted the following:

maddog 2 wrote:

I run a 25 on the front these days, for more grip.

I presume the implication is that they're running 23 on the rear, I may be wrong on that. I was confused about the logic of running wider tyres in front. The pressures would have to be vastly different between front and rear.

gasman_dave

I've had problems like this as well. I'm now 196 pounds so not overweight but it puts a bit of pressure on the back.

Conti 4000s were very smooth but I found they cut up badly - I think the local roads in the West of Scotland are made by tossing granite chips onto melted tar in the main.

Michelin Pro Race 3 cut way too easily and wouldn't go back.

Got recommended Vredestein fortezza tricomp by one of the riders from Lomond Racers CC. I changed to them last February and have been really impressed. They have a pressure range of 115 - 145psi for the 23mm so they may be what Ross might try.

I,ve had one pinch puncture with them but I went out with a soft front and hit a hole. That is all in 15 months, 2 Etape Caledonias and lots of riding in-between.

Dave

scottarm

attached link has a guide for pressure and also a tyre selector dependant on your typical ride

http://www.vittoria.com/tech/recom-tyre-pressure/

cougie

A few years back I would ride vredestein fortezza tri thingies at about 140 psi.

Until i hit a submerged pothole and blew out both tyres. Neutral service was continental so i ended up with two GP4000S tyres. Mechanic said not to go over 100 PSI. I havent looked back since. My last p******* was when the inner tube perished !

tonyf34

A larger front tyre gives you better comfort and more traction in corners, one should NEVER have the same tyre pressures front & rear if you have the exact same tyre on.
The graph linked to didn't just come about from guess work, it was done with scientific study, the original article was done by Frank J Berto published in Bicyle Qrtly magazine some years back, here's a link to an excel spreadsheet that helps you work out what the graph is saying http://www.biketinker.com/2010/bike-res ... -bicycles/

RossMu

I run with 23's both front and rear. The only time I can recall having a flat on the front wheel is when I got a pinch-flat after hitting a pot-hole at 20+MPH. As gasman_dave mentions, the roads are pretty poor; generally it is shards of glass that I am picking out the tyre when doing repairs. Need to look at the wider tyre option as well - thanks!

BrianTrousers

tonyf34 wrote:

A larger front tyre gives you better comfort and more traction in corners...

I switched from 23's to 25's. Does this mean I now need to put a 28 on the front?

To echo some of the other comments, I weigh 200lbs but I'm not overweight as I'm 6'2". If you're 200lbs and are overweight because you're 4'6" your rear tyre won't know the difference anyway so don't worry about it.

Did see an American documentary the other week where they put this obese chap who was around 400lbs on a bike and tried to make him ride 100 miles. He kept puncturing with pinch flats and they had to pretend it wasn't because he was chubby.

Sleeping_menace

I'm a bit of a big old beast myself, (115kg), and I run the Conti GP4000S's at 120r and 110f.. I'm going to curse myself by saying I've not suffered any punctures for ..>2 years..
I really think it's much more about avoiding road shrapnel when possible than it is about tyre width or particular brand..
The previous Vredesteins I ran gave me similar results to the Contis (no punctures), but I did run those at 130 f/r as they simply felt better at that psi..