One bike for climbing, one for descending?

[Garry Booth]

Is there a case for eg Tour riders switching bikes at the top of a climb for the descent? There must be design tweaks that could make a bike better for going down than going up, and vice versa. I'm guessing they would have done it if it were possible. But maybe people have some ideas!

[kylecycler]

Peugeot used to do it in the 1970s, certainly. If you download a copy of 'The Custom Bicycle' - a wonderful book - from the Classic Rendezvous site...

http://www.classicrendezvous.com/public ... icycle.pdf

...and scroll to page 122, you'll find this (remember this was in the '70s - I've no idea what goes on nowadays, although the first paragraph still holds true):

Most professional riders request the shortest possible chainstays and the smallest frame possible. Frequently, riders select a frame that years ago would have been considered too small for their physique. The popularity of the small frame is simple: the smaller frame is usually stiffer.

The ideal design that Saugier [head of technical research at Peugeot bicyles at the time] and his colleagues use for the professionals is composed of 73- to 73.5-degree angles. They then vary the fork rake [/offset] and the caster [/trail]* for the use of the bicycle. Usually a professional racer will have several bicycles and if possible will have a bicycle with a 30- to 35-mm. caster for climbing compared to a 75-mm. caster for downhills.

Although the shorter wheelbase gives a stiffer ride, there have been problems with high-speed handling, particularly when descending large mountains. To remedy this, Peugeot supplies the team riders with bicycles that have a greater degree of caster for long mountain stages.

At Peugeot, they believe that the caster determines steering ability and stability at high speed. The caster dimension can be increased in basically two ways: by decreasing the head angle or increasing the fork rake. According to Saugier, the ideal for the team professionals is to have 73-degree parallel angles which give the ideal length top tube (this refers to standard-size frames—not the smaller or the larger frames). This is ideal when combined with a fork rake of 35 mm. and a caster of 70 mm. This design is specifically intended for racing, however.

One sentence in the last paragraph isn't quite correct: Caster (trail) can be increased in basically two ways: by decreasing the head angle or decreasing - not increasing - the fork rake. Increasing the fork rake would decrease the trail. It's confusing!

*With bicycles, caster is more commonly referred to as trail, although they're the same thing, just as rake is the same thing as offset.

AFAIK 'optimum' trail for a racing road bike is considered to be around 60 mm - that way you get a jack-of-all-trades, at least for tyre widths from around 23 to 28 mm. Wider tyres have 'pneumatic trail', which means they work better with less geometric trail.

Basically, low trail is more stable when climbing, especially when out of the saddle - the bike tends to be very inert, doesn't respond to lean, just steering, and as long as you don't steer, it tends to stay straight and go nowhere other than up - whereas high trail is more stable and less twitchy at high speed - motorcycles have around 80 mm of trail, but their speed parameters are obviously a lot higher. Mountain bikes work best with high trail, apparently, but you want them to be 'jinky' at low speeds, the opposite of what you want a road bike to be when climbing Mont Ventoux. That's my interpretation of it, anyway, but it's such a complex subject I might be wrong!

If that all sounds like the old Abbott and Costello sketch "Who's On First?" (I hadn't a scooby about any of it myself until a couple of years ago) I'll knock up a couple of illustrations later to show you what high and low trail look like, but I'm away out on the bike now.

The likes of Brucey and 531colin know more about this stuff than me and have vastly more experience, so they might chip in if they see this thread.

(I just hope Peugeot's 1970s set-up wasn't what prompted you to ask the question in the first place, or I've just wasted an awful lot of time!)

[Garry Booth]

That's really interesting. And if it's not a dumb question, is there anything to stop a rider being given the bike with a downhill frame as (s)he crests the mountain? And then, swapping to the uphill bike for the next ascent. Maybe the changeover would cost too much time in a close race.

[RickH]

My understanding is that the rules don't allow for a pre-prepared changeover - i.e. someone waiting at a pre-arranged spot with a bike - so the rider will have to signal to their team car, which on a mountain stage is a very variable thing time wise as team cars can get stuck some distance behind riders.

The bike change strategy has, however, been used a few times on mountain time trial stages that don't have a summit finish to switch from a climbing bike to a TT bike at the crest of the main/final climb - the rider still has to signal for service but they will have their own car following immediately behind & the changeover will have been pre-planned - to take advantage of the aero advantage of a TT bike on the fast finish.

Rick.

[Redvee]

I'm pretty sure I saw Sir Brad 'swap' bike cause of a mechanical issue during a TdF mountain ITT but can't find anything on Youtube.

[Postboxer]

I thought Chris Froome did it in 2013, there was debate as to whether the mechanic should have been allowed to give him a push start, as he had elected to swap bikes but had no mechanical problems. Here's an article-

http://velonews.competitor.com/2013/07/ ... ial_295701

I've often wondered whether any bottles and clothing handed to riders at the tops of climbs are really just weights, to give them an advantage descending.

[Garry Booth]

Yes I believe loading up with bottles is a way of adding to momentum.

[Garry Booth]

Interesting article Postboxer. I like how they weigh the advantage of the different bike against the time taken to changeover and figure that 15sec net makes it worthwhile!

[honesty]

They are allowed pretty prepares bike swaps, a number of pros do it on Paris Roubaix for the longer cobbled sections towards the end.

I'd definitely more interested to see what the rules are on taking on 2 "water bottles" full of lead were and whether you could take on enough weight to give a significant advantage...

[Postboxer]

Marginal gains!

Osmium weighs twice as much as lead, 22.6kg/litre, so if your frame and bottle cages could take it, a couple of bottles of it would add a huge weight to an elite racer on a superlight bike. Assuming you could actually get them on the bike nonchalantly. It might be too much extra weight that it would seriously affect handling, but it would certainly help downhill.

[mig]

i seem to remember jan ullrich doing this in a tour TT with a long hill towards the finish. IIRC correctly he switched to a TT bike with a rear disc just before the summit where his velocity was low to reduce the time slowing and standing still..
https://www.youtube.com/watch?v=nfgmuZUQqcg

i think it related more to the speed downhill though.

(this wasn't the main thing that made him fast that year. )

[mercalia]

Is there a case for eg Tour riders switching bikes at the top of a climb for the descent? There must be design tweaks that could make a bike better for going down than going up, and vice versa. I'm guessing they would have done it if it were possible. But maybe people have some ideas!

yes the one for going up hill has a bb motor in it

[iandriver]

Swapping bikes is common place on mountain TTs. http://www.cyclingweekly.co.uk/news/rac ... rial-27508

[pete75]

Jean Robic, winner of the 1947 tour, was only 5' 3" tall and just over 9 stone. He would use a drinking bottle filled with lead shot to aid his descents.

There's also this tale from the 1963 tour

'Jacques Anquetil is a bona fide Tour de France legend but even he wasn’t beyond a bit of foul play. In his day, the rules didn’t permit riders to change bikes unless they had a mechanical problem. So when the Frenchman’s team director Raphael Geminiani thought he could do with a lighter bike for the Col de la Forclaz, for stage 17, he told a mechanic to cut through a gear cable, claiming that it had snapped.

Jacques anquetil's rule-bending towards the end of the '63 tour helped propel him to a third consecutive title:

The bikes were switched back at the summit and Anquetil snatched a sprint victory over big rival Federico Bahamontes, catapulting himself to the top of the GC on his way to his fourth Tour crown. The rule about swapping bikes was scrapped ahead of the race in 1964.'