What makes a bike fast?

[Electric Panda]

26FS is fast -> Sauser World Cup
29FS is fast -> Kulhavy World Cup
26HT is fast -> Absalon World Cup
29HT is fast -> No World Cup winner yet but plenty of podium success
650B HT is fast -> As with 29HT getting recent success

So wheelsize is important but not really a determining factor.

You know there is no use comparing XCO wheelsets... The factory teams that race anything heavier than 26 all have 'one race only' wheelsets that are as light as the 26 next to tehm on the start line. The teams all use powermeters and know already that if they use 11% heavier wheels and tyres they will be around 7% to 8% slower - the same figures that keep appearing in non team tests

Better to compare real world results of power tests from bikes that you can conceivably buy... ie if the wheel dia is 11% bigger it will be at least 11% heavier, probably more as the bigger dia will require more weight to make it as stiff due to the greater leverage. eg Easton 29 carbon is 14% heavier than their 26 carbon

Weight in the wheelset/tyres is critical to a fast bike and everything else being equal, will be the determining factor

 

[jathanas]

You know there is no use comparing XCO wheelsets... The factory teams that race anything heavier than 26 all have 'one race only' wheelsets that are as light as the 26 next to tehm on the start line. ...

E.P, I'm going to have to call BS on that one. Mostly stock parts on this racing Stumpy: LINK

 

[Electric Panda]

Jathanas. You give the impression of having been around racing awhile. Do you race vets? For some reason I got that idea.

Anybody in this industry, and any other with corporate input, will tell you that anything, anything at all, that is a publicity shot n’ show is done by the marketing dept. ... including that piece you linked to. If you really want to know what the guys and girls are riding then show up to a race... or ... there are two coaches and two team wrenches who post on MTBR in the XC forum fairly reguarly. Everybody knows them and it is no secret who they are. As an example, Cathy Pendrel’s bike was shown once with very different wheels and tyres than she uses. She - and a few others - ride mavic carbon compression spoked wheels that are just not available on retail so they show other Mavic wheels instead.

It is no great secret that Specialised, Trek, Scott and probably Giant (although I don’t have knowledge of Giant) all do things like shave carbon rims, nipples, all ‘dross’ is shaved off tyres, all tyres and rims are pulled off the line to get lightweight stuff ... all to get weight down to below the 1200‘s where the 26 wheels are generally speaking. There is an ex wrench in the Melbourne race scene - which I think is where you are - will tell you the same. The two XCO coachs on MTBR make no bones about it and the Subaru wrench is also open enough on weights and tyres. A 29wheel at this weight has a limited life - one race at this level. Mostly the carbon rim is reused the spokes etc is binned. Obviously it is only the big factory teams that can do this reguarly. Tyres are so important the testing of them - and on each course - is a major part of a teams job.

BTW you once posted a media release where Specialised claimed they test and race tyres inflated in plus or minus 1/2psi increments. Quote from the current World Champions coach - after open laughter. ‘you would have to see the factory’s (team) media programs to understand the scope. What would be the point of 1/2 psi increments anyway? ... anything you see in a magazine is just for selling bikes - that is what they are for afterall'

 

[pharmaboy]

You know there is no use comparing XCO wheelsets... The factory teams that race anything heavier than 26 all have 'one race only' wheelsets that are as light as the 26 next to tehm on the start line. The teams all use powermeters and know already that if they use 11% heavier wheels and tyres they will be around 7% to 8% slower - the same figures that keep appearing in non team tests

Better to compare real world results of power tests from bikes that you can conceivably buy... ie if the wheel dia is 11% bigger it will be at least 11% heavier, probably more as the bigger dia will require more weight to make it as stiff due to the greater leverage. eg Easton 29 carbon is 14% heavier than their 26 carbon

Weight in the wheelset/tyres is critical to a fast bike and everything else being equal, will be the determining factor

So if there is a 7 to 8 % advantage - any team with a few grand per rider, could race a 26er with a a one race only wheelset and win

But they choose not to - the only ones desperate enough are the 29er teams?

Why are the 26er riders choosing not to put their best foot forward and winning against the 29er by using an equally light wheelset (per inch)?

 

[jathanas]

Peace E.P.

I disagree with your view on 29ers. But lets not derail this thread. My post was really about the factors that i consider to make a bike fast. My opinion is that 26er or 29er is not that much of a factor. I stick by that.

I enjoy reading your posts btw.

Cheers mate, Jim

 

[Electric Panda]

Pharmaboy

When Scwhartz (Motorola domestique) was asked why 98% of Americans believed Armstrong raced cleanly he replied it was because 98% of Americans didn’t know anything about elite sports.


“a few grand per rider” ROFLMAO !!
Have you any idea how many manhours it takes Specialised to weigh and pull rims and tyres from a manufacturing line?! Here is a clue. When Schurter (Scott) was racing 26s he apparently raced 1kg wheelsets. The rims were ‘pulled from the line’ Swedish ones at around 230g each - thats right - about 80 - 100g less than retail DT Swiss stuff. The cost per rim was about 2000euro at the time and he was cracking a lot of them.

A team can easily spend 1500 to 6000euro on an average set of race wheels multiply that by number of races if you are ditching them every race, + spares, per rider and you have a massive bill. Add in handbuilt tubs of 10 sets per rider per month if your team is able to go that way and it is pretty easy to see some big numbers. No problem for a tier one road team - even some tier 2s have big budgets... but mtb?! not a chance... only the factory teams have that kind of budget. And factory teams are only there to get image to sell bikes. And the bikes the big guys are selling right now is 29... and they are willing to spend massive sums to convince punters to buy their bikes and it is not much point selling 26s when everyone already has a couple of those. But don’t worry Pharmaboy - 650 is coming next

Have a look down the start list of the next XCO race then search the homepages of a few of the little teams after about 20th place. These guys run on a shoestring and struggle to get airfares together. While you are there check how many of the little guys run 29s.... hint bugger all... sure some of these guys run lightish wheelsets but they have to last more than a few races...

Ever wondered why only a very few of the girls race on tubs? cause most female mtb teams run on hope and not much else. 200 to 400 euro on a set of tubs? that you need 10 of? ... no way pal. guess how many girls ride 29 that aren’t in a factory team... one - Maja W - and she rides tubs also... she must be making a bucket load from those photo shoots

 

[Electric Panda]

Peace E.P.

I disagree with your view on 29ers. But lets not derail this thread. My post was really about the factors that i consider to make a bike fast. My opinion is that 26er or 29er is not that much of a factor. I stick by that.

I enjoy reading your posts btw.

Cheers mate, Jim

mate anyone in a race team would agree with what you posted re stiffness etc.

but a heavier wheelset/tyres? ... only if they are employed to say so

 

[pharmaboy]

EP, you are still left with any team with a reasonable budget being able to win by running 26ers at the same amount of effort and $'s as they make for the 29ers. I reckon Scott would rather win on a 26er than have trek or spesh win on 29 - unless there is a conspiracy? Marketing depts want podium shots for their next print adds, 2nd place doesnt cut it, it needs to be first, and the bike wheel doesnt need to be in shot, you just need your rider on top.

 

[jathanas]

mate anyone in a race team would agree with what you posted re stiffness etc.

but a heavier wheelset/tyres? ... only if they are employed to say so

Rotational weight is huge, i'll grant you that one. There is a limit though. At some point you'd be racing a noodle.

I'd back a strong athlete to get better results from a wheelset that is both stiff and reasonably light.

No one races with heavy wheels these days.

 

[hungrytiger]

The teams all use powermeters and know already that if they use 11% heavier wheels and tyres they will be around 7% to 8% slower - the same figures that keep appearing in non team tests

Hi , I'm just interested. By slower, do you mean slower acceleration? Are there any references for the figures you're quoting?
thanks

 

[daddyrat]

the rider and only the rider hahahahaha

 

[Electric Panda]

EP, you are still left with any team with a reasonable budget being able to win by running 26ers at the same amount of effort and $'s as they make for the 29ers. I reckon Scott would rather win on a 26er than have trek or spesh win on 29 - unless there is a conspiracy? Marketing depts want podium shots for their next print adds, 2nd place doesnt cut it, it needs to be first, and the bike wheel doesnt need to be in shot, you just need your rider on top.

Corporate marketing strategy doesn't work that way. In bikes, everyone has 2 x26's and sales were slowing - ask your local LBS. Scott had a 1st and 2nd in 2010 on 26FS - unprecdented - yet changed to 29 to get momentum in the sales room.

In the Pros/Cons of 29s thread I presented/quoted and linked studies on power regarding 26/29 and tyre volume, professional views and observations of two WC XCO coaches, two wrenches who are now working or have worked on WC XCO teams ...

Thru all this you posted your opinion... not one fact, not one study or professionals judgment to the contrary.

You seem to be still struggling with the fact that a shallower incidence angle/volume of a 29 will not overcome the additional weight of an off the shelf 29 wheel/tyre.

And struggling with the fact that WC XCO don’t use off the shelf 29 wheel/tyres

I showed studies with multiple riders, multiple courses, over multiple days all you could do was argue over what ‘published’ means... or complaining that the figure of 7% must be too high because you think it is...
(For those who are bright enough not to go near the 29forum and insinuate their bikes and 650s are mostly a marketing exercise when it comes to speed but are interested in the studies etc... http://www.rotorburn.com/forums/showthread.php?236632-Pro-s-Con-s-of-the-29er/page2 and starting again at http://www.rotorburn.com/forums/showthread.php?236632-Pro-s-Con-s-of-the-29er/page8 )

If you think the figure of 7% is a lot for an added 14% of wheels and 11% tyres and tubes/sealant ...
Why has not Speccy/Giant/Trek/Scott/whoever made available some of the thousands of hours of power figures they have to counter those studies?
Rather than Specialised getting an employee to ride a hill a couple of times with a HR monitor on his race bikes and sticking it on Youtube – if normal off the shelf 29s are indeed inherently quicker or even the same - why wouldn’t they just grab a power meter from their semi trailer of equipment and ride with that?
Why did no-one in WC XCO start racing 29ers till the factory teams got on board?
Why amongst the 200 or so starters in mens and womens WC XCO – save for a few - are generally only some big factory teams racing 29s or 650s?
What percentage disadvantage do you think it would be to add 50gms a tyre for sidewall protection?

If you gave a passing thought to those questions how about being able to find some positive data on ...
Any test results of at which point tyre volume - and therefore mass - becomes a disadvantage - that is, the crossover point?
What about incidence angle - happen to come across anything that might give an indication of the actual effect of this in percentage gain? Incidence angle being the only thing effectively different between 26/29/650 once tyre volume and wheelset weight is taken out of the equation – two things easily manipulated.
Any ideas on the 'retarding lever' percentage gain/loss of the different shaped contact patch? Tyre contact patch is going to be different between 26/650/29 for the same volume and therefore the same potential psi

These questions are related... Over the last 4 mths I have been sent power data for different analysis (nothing to do with tyres etc rather robustness of an aspect of the data collected)... everything from ht v softail, normal sidewall v heavy sidewall, tubs v skinnys, high pressure skinny v lower pressure baggies... different courses for some, particular courses for others... 26 on tubs v 29s on skinnys v 26 on baggies on one particular course, 29 on skinnys v 26 dually v 26 softail... grippier tyres v wider low knob tyres on a variety of courses... and a bunch more ... all on race wheels with very fast, obscenely skilled guys/girls on WC courses or equivalent test courses ... smallish data sets and of no relevance outside WC XCO ... obviously (although probably not to you) nothing comparing 26 or 29 wheels that you and I can buy.

The point being that if you have anything at all that passes for data regarding off the shelf 29s, any data at all, that even sniffs of fit for purpose, has a mention of methodology and a passing interest in control then the good folks here who are into racing would love to hear about it.

Remembering this post is about speed on short course XC. Marathons are different where comfort becomes important.

Regarding WC XCO – the range of tyres and wheel weights is quite amazing. There are girls racing Furious Freds and Ikons with sidewalls on the same cct, it really is all about race tactics – where a rider/coach think there may be advantage on a particular section and how the rider thinks the race may unfold.