Not much faster on a cyclocross than a mountain bike

ClubSmed wrote:

ClubSmed wrote:

Chris James wrote:

If the commute is mostly on road then road tyres are suitable. Knobbly tyres at 90psi probably give less grip than slicks tyres because there is less tyre material in contact with the road.

The important part to note of this is IF the commute is mainly road. Having just got back now from cycling along a canal path through what looked like frozen snow (though I don’t remember it snowing) I think my 90psi knobbly tyres gripped through it far better than slicks. That sort of situation is only going to increase over winter so I’m certainly going to stick with what I’ve got until Spring. If the OP has a similar commute I suggest he do the same

But you would get so much more grip running your knobbly tyres at a lower pressure.

Obviously tyre choice should be appropriate to the surfaces that you will be going along. The OP said his route was urban roads and park tracks, so sounds like it is mostly, perhaps totally, tarmac. I know leaves have been mentioned earlier but these just require a bit of care, in the same way as wet surfaces, not a different tyre. My shared use path section is currently covered in leaves and I ride along there at 20mph in the pitch dark. The canal tow path is actually made easier by leaves as they fill in the surface irregularities and give a more forgiving ride.

Knobbly tyres at 90psi have a lot less grip on wet corners on the road than a road tyre though. In fact they are explicitly banned as dangerous from level 2 road and time trial activities by BC because of the lack of grip.

I don’t think you said how

I don’t think you said how wide the tyres were on your crosser?  

You did say there is a steep hill up the North Downs (not Pebble Hill is it?!).  I would have a look at your segment times up this hill, I would expect this is where you are getting the most benefit from the cx bike, assuming it is significantly lighter than the mtb.  If you have a lot of stop/start traffic, then that will really nullify the higher cruising speed you would expect on the cx bike.

I only have a road bike and an MTB, most of my mates have all three types.  When we do off road routes, they sometimes use their cx bikes, and I really find I struggle to keep up with them, unless I have picked the route and gone for an evil amount of muddy hard climbs (!)  As far as I am concerned, a cx bike should be faster than an MTB on mainly paved roads.  It should also take considerably less effort to ride at the same speed as an MTB.

The examples you posted showed 0.7 mph average speed increase, 5% is not to be sniffed at in an hour.

antigee wrote:

fair comment I dismissed the headline figure as that was at a very low psi – irrespective may be look at the road tyre numbers rather than touring tyres? 

I would agree if the OP was only commuting on the road but it is a mix of road and park paths that they are using so a fair bit of grip will be needed. You do not want to be battling leaf mulch and ice through park paths in the Autumn/Winter with slicks!

I commute in the winter with Kenda Small Block 8s as I use mainly canal paths and park cycle routes and am very glad of the extra grip at this time of year!

Quote:

ClubSmed [86 posts] 1 hour ago
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antigee wrote:

 

pretty sure kenda small block 8’s have their place but not for riding on the road – rolling resistance is the issue  – one option with a cx is to run two sets of wheels one for road speed, one for dirt – anything else is a compromise 

http://www.bicyclerollingresistance.com/mtb-reviews/kenda-small-block-ei…(link is external)

 

Actually I don’t believe that the review of the Small Block 8 on that site is fair. I, and the original poster of this, run the Kenda’s at ~90 psi (which is around the manufacturers recomended) and they were tested at a much lower psi on the site. If you take the 45psi rating and compare it against the touring bike tyre charts at the same psi the Small Block 8s actually come up on the top half of the table so I don’t think that rolling resistance is as bad as the site would have you believe.

The rolling risistance of 27 at 45psi according to the site makes it better than:

Continental    Top Contact II @ 28.4
Continental    Contact II @ 28.9
Schwalbe    Marathon Racer @ 28.9
Continental    City Ride II @ 29.8
Schwalbe    Marathon Plus @ 28.9
Schwalbe    Marathon Mondial Evo @ 38.6
Vredestein    Perfect-E @ 32
Vittoria    Randonneur @ 38.9
Continental    E.Contact @ 39.4

fair comment I dismissed the headline figure as that was at a very low psi – irrespective may be look at the road tyre numbers rather than touring tyres? 

Just to throw another thought
Just to throw another thought into the ring. Your MTB could well be quicker as MTBs tend to have gears that are accelerate fast i.e. low ratios. Wheres as the crosser will have higher gearing to cruise. A full blown race bike would have higher gears to cruise even faster.
Example
My mtbs have 22/34/44 and 26/40 on the front, low enough I hope t oget my up hills but absolute buggers to keep rolling at 20mph with spining faster than jet engine.

My road bikes are fitted with 34 or 36/50. They don’t go up hills or accelerate faster but are easy to keep rolling at 20mph. I’ve also tried 39/53 and struggled on hills and felt it took an age to get up to speed but cruised very nicely.

So what maybe happening is that the commute may involve a lot of stop start so the mtb is accelerating faster due to the lower gears but thecrosser cruises. As you have stated in you original post.

Bottom line they are two different beasts designed to do different things. Stop comparing them.