Effect of tyres on speed?
Effect of tyres on speed?
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Marcellus

Original Poster:

7,204 posts

248 months

Thursday 7th March 2013
quotequote all
I'm currently car-less so needing to cycle to my sailing club which is not a big issue really as it's only 10 miles.

Anyway, I did a trial ride on my road bike and was quite happy with the 33minutes considering I've not ridden anything for a couple of years

I need to go to my club on Saturday and the weather looks wetso here's my dilemma.

I haven't ridden my roadie in the rain for about seven years since I had a big crash in the rain the effects of which I still suffer. So when it's raining and I've wanted to go out on my bike Ive gone on my mountain bike, but changed where I road, ie went up the mountains and came down the pistes as opposed to road riding.

Obviously to get to the club I haven't got the luxury of changing my route.

In the garage I do have a set of slicks which I could swap onto the mountain bike but I've never ridden on these hence the question to you all.

If I can ride 10miles in 33mins (so an average of 18.1mph) what speed am I likely to be able to average on a) knobblies or b) slicks on the mtb?

Or should I just refer to rule #5 and mtfu and get over my fears of crashing again?

scottri

951 posts

211 months

Thursday 7th March 2013
quotequote all
I guess you'll see 1-2mph drop using MTB on slicks and another 1-2 mph if you have knobblies on.

Edited by scottri on Thursday 7th March 18:53

upsidedownmark

2,120 posts

164 months

Thursday 7th March 2013
quotequote all
Perhaps a little more of a penalty for the knobblies.

Personally I'd MTFU and take the road bike, just don't 'push it' - aside from the misery of being soggy there's nothing inherently dangerous about road bikes in the wet.

What particularly is worrying you / how did you crash? Even slick road tyres should offer plenty of grip in the wet (conti gators are the only ones I'm suspicious of, and that's only due stuff I've heard).

Marcellus

Original Poster:

7,204 posts

248 months

Thursday 7th March 2013
quotequote all
Thanks for the rough guides.. So my 33minute easily becomes 45 so mentally a half hour ride becomes an hour..... Think it's time I drank from the font of mtfu and got on with it.

Where it all went wrong before was 40+mph in the wet (downhill slop) 90degree right with a manhole cover, lost front wheel and the 1st thing to hit the ground was my hip..... Still have the damage, pelvis has never been straight since and as a result my back is still not good.... So for 7 years have avoided riding the road bike in the rain and now have this irrational fear that it's got no grip.....

neilski

2,563 posts

264 months

Thursday 7th March 2013
quotequote all
Rule #5 and just don't go mental in the wet.

Gizmoish

18,150 posts

238 months

Thursday 7th March 2013
quotequote all
Manhole covers are lethal at 5mph or 40mph.

The contact patch of a road slick is about the size of a 5p. The contact patch of a knobbly is the size of the knobble that's touching the ground at the time...

TKF

6,232 posts

264 months

Thursday 7th March 2013
quotequote all
Hey Marcellus. It's the artist formerly known as thekirbyfake here biggrin

I find it's not just the tyres that'll be holding you back. More upright position, bouncy suspension and weight will also hurt speeds.

upsidedownmark

2,120 posts

164 months

Thursday 7th March 2013
quotequote all
Marcellus said:
Thanks for the rough guides.. So my 33minute easily becomes 45 so mentally a half hour ride becomes an hour..... Think it's time I drank from the font of mtfu and got on with it.

Where it all went wrong before was 40+mph in the wet (downhill slop) 90degree right with a manhole cover, lost front wheel and the 1st thing to hit the ground was my hip..... Still have the damage, pelvis has never been straight since and as a result my back is still not good.... So for 7 years have avoided riding the road bike in the rain and now have this irrational fear that it's got no grip.....
So, erm.. realistically you'd have gone down on the mountainbike, roadbike, or possibly even a motorbike! Easy for me to say I know, but I think it's a bit daft to avoid the roadbike on that basis - they're really not that bad in the wet, and you're 7 years older & wiser smile

JustNeil

636 posts

256 months

Friday 8th March 2013
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Yup, you'd have hit the ground on a motorbike too. Wet manhole covers are mentioned constantly in bike circles as being lethal and avoided at all costs, so regardless of which 2 wheels you chose, you'd have gone down.

Why not try a trial run the next time it rains, just round the block, to see how you get on? If it's horrible, then get the mountain bike out instead, but at least you'll be close to home.

mchammer89

3,127 posts

242 months

Friday 8th March 2013
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Gizmoish said:
Manhole covers are lethal at 5mph or 40mph.

The contact patch of a road slick is about the size of a 5p. The contact patch of a knobbly is the size of the knobble that's touching the ground at the time...
The contact patch isn't everything though. The movement of those tread blocks also generates grip.

Marcellus

Original Poster:

7,204 posts

248 months

Friday 8th March 2013
quotequote all
All good poitns, so rule #5 being applied, it's just I think tbh I've made more of it that it really was.. don't get me wrong nasty fall but since then the fear of falling again has been greater than the actual risk of falling if that makes sense..

In a way I do hope it's absolutely pissing it down when I need to cycle to work in teh morning and as I've got no option than to ride I'll just get my head down and get on with it.

I did go out for a trial on the MTB (with knobblies) today to see what sort of speeds are "maintainable" and they too low to consider... it wasn't the suspension (I can fully lock it out) nor the riding position being more upright but it's the gear ratios... I was in top (or bottom I never know) and by the time I got upto 18mph legs were spinning like to top so not sustainable (for me at the moment anyway)

ecsrobin

18,662 posts

194 months

Friday 8th March 2013
quotequote all
Another big affect with the MTB is the tyre pressure generally you'll be running them softer for being off road so put a lot more air in to assist yor commute time and any suspension you have lock it off or if you don't have that luxury put it on its hardest setting so your losing as little energy as possible.