# Does under inflated tyres make a difference...



## ray316 (4 Aug 2013)

As l have put in the topic thread under inflated tyres, what effect will this have on road cycling..
The reason l ask is l have been out today and did 16 miles and found it hard going and my speed seemed to be slower, got back home and felt the tyres and they was quite soft on front and back..
l left them for a few hours just incase l was unlucky enough to have slow punctures but they did'nt go flat so l put more air in both tubes... 
What should a road bikes air pressure be.. MIN ans MAX...
Will it effect my speed with under inflated tyres..


----------



## Cycleops (4 Aug 2013)

It will make a big difference, under inflated tyres will suck you onto the road and slow you down by offering increased rolling resistance. Always inflate to the max indicated.


----------



## PocketFrog (4 Aug 2013)

ray316 said:


> What should a road bikes air pressure be.. MIN ans MAX...



It should give you the min and max pressures on the sidewall of your tyres - it will be slightly different for each type of tyre



> Will it effect my speed with under inflated tyres..



Certainly, the amount of surface area touching the road is increased and therefore rolling resistance is also increased.


----------



## jim55 (4 Aug 2013)

depends on the size of the tyres as a rule the bigger the tyre (mtb type)the less pressure ,usually in the region of 60 -85 psi,as opposed to road bike tyres(wee skinny ones,23 or 25 ish size )usually they are in the region of around 100-130 psi
and yes ,under inflated tyres will affect ur ability to roll ,so in short ,max pressure if you can


----------



## Lanzecki (4 Aug 2013)

Yes it'll effect you a lot.

http://www.dorkypantsr.us/bike-tire-pressure-calculator.html may help.. 

But everyone seems to run different pressures.


----------



## JoeyB (4 Aug 2013)

I massively notice a drop in tyre pressure on my road bike so would say under inflating makes a negative difference.

I need every small win i can get to turn those pedals!


----------



## JKility (4 Aug 2013)

Yes

Less pressure will make that the tyre is softer and there will be more contact with the road surface slowing you down as well as more friction.


----------



## Hill Wimp (5 Aug 2013)

Oh boy does it make a difference


----------



## byegad (5 Aug 2013)

I used to run my tyres at or close to maximum pressure, then lost a lot of weight, so now run at around 90% of maximum pressure, which is not only smoother but actually faster on a rough road.


----------



## DWiggy (5 Aug 2013)

Oh yes


----------



## PhunkyPhil (5 Aug 2013)

If the surface of the road is wet or loose lowering your pressue will improve grip but at the result of speed because of the extra roling resistance.


----------



## Davidc (5 Aug 2013)

Always stick with pressures in the range stamped on the tyre wall. Buy a gauge (cheapish one). To be on the safe side stay 5 psi below max or 5 psi above min.

Then as above. Higher pressure usually gives easier running, lower is more comfortable. Experiment to find the best compromise and recheck pressures at least once a week.


----------



## byegad (5 Aug 2013)

PhunkyPhil said:


> If the surface of the road is wet or loose lowering your pressue will improve grip but at the result of speed because of the extra roling resistance.


 
IF the tyre is so hard you get chatter on a rough road you are wasting power, in effect the power to move the bike up and down is coming from you. Taking just a little pressure out will allow the tyre to absorb the chatter and so you go faster. Go too low and you merely add rolling resistance so it's a fine line.


----------



## Gravity Aided (5 Aug 2013)

Plus, you run the danger of "Pinch Flat", when the tube gets trapped between the rim and the road in an unproductive way. Manufacturers specifications always work best, it seems.


----------



## Boon 51 (5 Aug 2013)

I dont weight a lot so run my tyres about 10% less which helps but running 25cc instead of 23cc also helps..


----------



## Shortmember (5 Aug 2013)

I just pump my tyres up until the handpump overheats or I can't push any more air in- whichever comes first.I'll put up with a boneshaking ride on rock hard tyres rather than the pedalling-through-treacle feeling that comes with underinflation.


----------



## HLaB (5 Aug 2013)

Depend on the surface, on a perfectly smooth surface it makes a massive difference IMO but less so on a rough one; however, if your tyres are too low pressure it doesn't really matter as to the surface tyres are just too sluggish. FWIW I run my tyres at 105psi rear 95psi front and they often fall by 10-20psi and I don't notice much change but if they fall further I do.


----------



## steve52 (5 Aug 2013)

mmm did the op really have to ask?.i noticed the differnce when aged about 7


----------



## byegad (5 Aug 2013)

Gravity Aided said:


> Plus, you run the danger of "Pinch Flat", when the tube gets trapped between the rim and the road in an unproductive way. Manufacturers specifications always work best, it seems.


 
Exactly for the minimum pressure, I'm talking about a small %age reduction in pressure only.


----------

