wider tyres:Less MPH

[knapdog]

In brief, I currently have 700x25 tyres. Could anyone tell me what differences in average mph I might encounter if I were to switch to 700x28? I am considering changing for extra comfort but have no idea what I would be sacrificing in speed. I'm training for 100+mile rides and currently average anything from 12.5 to 15 mph.

 

[MacB]

all other things being equal then I'd be amazed if it made any more than 0.5mph difference

 

[montage]

0.5mph is a fair bit over 100 miles...

 

[RedBike]

They could be quicker, seriously!

28mm tyres should, all things being equal, have a lower rolling resistance at any given pressure than a 25mm tyre.

However, in practice you will probably run a 28mm tyre at a lower pressure than you did your 25mm tyres so they wont actually roll quicker.
And...
The tyres will be heavier and that extra weight will slow you down accelerating and while climbing.

Go for a high quality 28mm tyre and there probably wont be any real notcable difference in your average speed. Traffic, head winds and what you did the day before are probably going to have a much bigger effect.

 

[oxford_guy]

I average 12-14mph on 35mm Schwalbe Marathon XR tyres on my tourer and am not especially fit, I don't think tyre width makes a huge amount of difference if you keep them pumped up, though acceleration may be slower for wider, heavier tyres

 

[oxford_guy]

This thread about rolling resistance and tyre width may help clarify things?

 

[Archie_tect]

Nope!

Low rolling resistance means the tyre is more efficient... yes?
So a tyre with a smaller contact area with the ground with higher pressure and a smoother tread rolls easier [ie with a lower rolling resistance] than a fat one with a chunkier tread pattern due to lower friction... yes? Less friction equals easier pedalling
for an equal amount of force and effort... yes?

Sounds logical....

 

[palinurus]

Not much. I use 28s on my commuter at the moment, I have used 23s (same type of tyre too).

If there's a difference in rolling resistance it isn't really noticeable. On bad roads the 28s seem better.

 

[gavintc]

They could be quicker, seriously!

28mm tyres should, all things being equal, have a lower rolling resistance at any given pressure than a 25mm tyre.
.

Presume, following your theory that all racing cyclists are using the wrong tyres.

 

[GrasB]

They could be quicker, seriously!

28mm tyres should, all things being equal, have a lower rolling resistance at any given pressure than a 25mm tyre.

However, in practice you will probably run a 28mm tyre at a lower pressure than you did your 25mm tyres so they wont actually roll quicker.
.

Presume, following your theory that all racing cyclists are using the wrong tyres. [/QUOTE]
Thing is all else isn't equal, you can make smaller tyres lighter for the same durability & cornering response, this very well make a bigger difference.

 

[accountantpete]

TBH Knapdog I don't think getting wider tyres will knock the speed at all - but it will increase the energy needed.

Personally if I were doing 100 miles plus I'd look towards getting 23's on a pair of light wheels so as to minimise the discomfort of climbing hills and headwinds and then look to make it more comfy "up top" - ie seat and handle bars.

 

[Fab Foodie]

In brief, I currently have 700x25 tyres. Could anyone tell me what differences in average mph I might encounter if I were to switch to 700x28? I am considering changing for extra comfort but have no idea what I would be sacrificing in speed. I'm training for 100+mile rides and currently average anything from 12.5 to 15 mph.

AFAIK...
At your average speeds there will probably be little difference between the tyre sizes. Narrower tryres come into there own when you travel at higher average speeds where aerodynamics play a part. Furthermore, narrower tyres are lighter so spin-up quicker when acceleration and hill-climbing are important too.
For my money I'd stay at 25 unless you feel you really need the extra comfort. Mind you, if you have mudguards they'll stuff the aerodynamics so you might as well have the fatter version! I'll do 100 miles in comfort on 23c Michelin PR3's at 110-115 psi but they're very supple tyres.
My final thought is maybe size is not necessarily the issue here, maybe tyre quality is the thing to be considered. I wrecked a pair of tyres on a 3 day trip and at a local shop could only buy some cheap 25c Oriums or similar and they were like riding on treacle whereas a 25c pair of Krylions is a much better ride and a 25c pair of PR3's would be even better. I feel tyres are an area of cycling where it's worth spending a bit of cash.

 

[jig-sore]

what no one seems to realise is that wider tyres have a larger side wall and therefore a larger circumference, this means that for every revolution the tyre will travel further. add this into the equation and it kinda cancels out the rest.

wider tyres will be more comfortable on the naff streets of the UK and will ride over the ruts and bumps far better.

I'm still averaging 16 -18 mph on my commute with 700x 40 tyres !!!!!!

useful link.... http://www.everydaycycling.com/edc/news/WiseWords/wise_words_tyres.aspx

 

[XmisterIS]

In my experience, when you're running 25's or 28's there won't be that much difference.

Strangely, though there seems to be a huge difference between 23's and 21's. I went from 23's to 21's and added about 2mph to my average speed!

 

[GrasB]

I take it this is after you've changed the trip computer's tyre circumference. What 21 tyres are you using? The only ones I can find look like very lightweight tyres which aren't likely to survive the junk on road surfaces I ride on.