time trial bike question

Hi folks,

I was utilising the search function just now to find out a bit more info about retro time trial bikes, not the small front wheeled, steep angled head tube time trial bikes but ones similar to the bike in the thread below

viewtopic.php?f=23&t=294628&hilit=Timetrial

Could someone clarify for me the differences between the bike above and a road bike. Obviously the differences between small front wheeled and steep angled head tubes time trial bikes and their contemporary road counterparts are as obvious as the difference between modern road and time trial bikes but for the life of me...........I actually can't see the differences between a retro road bike and the time trial bike in the pasted thread. They are just too subtle.

Can someone help?

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Typically the differences are small but things like:

Short as possible wheelbase: back and front wheels tucked into frame as far as possible - 'track like' fork rake, vertical rear dropouts or track dropouts as you are not really going to be adjusting wheel fit as your bestest tyres are going to be there for testing. The frame angles will be steeper more in the 73-74 deg range (estimated as frame size can affect that).
Minimal add-ons: Often single gear lever fittings (as often single chainring) perhaps one bottle cage. That frame in your thread has nice rear stays that are integrated into the rear of the frame, which wasn't that common and was seen as sleeker / would have been harder to build perhaps.

Weight: Usually if its custom built as a TT bike, the tubing would be perhaps on the thinner guage side of things to get some weight out of the frame. Tyres light as possible, possibly some drilled components etc, less spokes in wheels, but largely as little as necessary on the bike to make it light and quick. Minimal gear gaps - 13-18 blocks and probably a 53 or bigger chainring.

I am sure there are more, the differences are often subtle but they make for very nice, clean bikes, but they were largely single purpose.

A good book with lots of pics of older TT bikes in it is 'Time Speed and Truth' by Peter Whitfield.

All that said, lots of people DID use their road bikes or trackbikes to TT so the term is perhaps more flexible until you get into the Lo-Pro type bikes etc.

Here's a few pics of my own mid 70's TT frame that I raced in the mid 70's. Made by Kevin Sayles when he worked for Bob Jackson.

Generally by the mid 70's road frames were 74 parallel or 73/73 geometry, Fashion dictated that TT frames were 75 parallel or 75/76 which made for quite a lively frame The main tubes are Reynolds but the rear triangle and forks look Columbus to me



There was never any need for 10 gears so there was only a braze on for the right lever and the left side of the frame was blank, The Brakes were so close the Weinmann 500's had to be altered a little, Campag Piccolo struggled and to save weight the brake centre bolts were brazed to the frame. The fgork crown is cut down so as to be unrecognisable.



The frame was sliced / diced / chopped to cut weight. Aende cut the tubes and left holes or glued in x-ray film Mine is simply chopped



if you look closely the seat stay is not flattened for an inner ring and we had to use a double axle to get even the outer ring to avoid the chainstay.



The steerer was cut so short headsets never had enough room for spacers.



And then we drilled holes in everything we could.......

All in all, the only thing we did that was aero was to crowch lower and tape our laces over

Shaun

^Great information. Really enjoyed reading that Shaun

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The pictures of Eddie Adkins' bikes halfway down this page may be instructive to OP- a lo-pro, '70s conventional TT, and 'Road bike' side by side built for the same fella:
http://www.classiclightweights.co.uk/bu ... ilder.html

The visual difference could be subtle, at least until the TT bikes went to extremes like the MKM 'Ultimate' for example.

I think the '70s 'Road' geometry standard was 39" wheelbase, 16 1/4" stays, 73deg. parallel, 1 1/4" fork rake? With that as a benchmark, a practiced eye could (can) spot frames in which those angles have been steepened, stays, rake, and wheelbase shortened, and brake/tyre/tube clearances reduced from 'close' (say about 1/2") to 'super-close' or even beyond to 'fag-paper'..

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Thanks for the replies. All very helpful and informative

I'm not sure if the bike in the thread I pasted has a more relaxed geometry than the other bikes, but in Shauns post I can clearly see that the frame is more compact than a road bike, the rear triangle is clearly different and seeing the Hearne bikes side by side like that makes it a lot easier to understand what the minuscule differences are.

Were these sorts of bikes more expensive than their road equivalents and what prompted the move to Lo-Pro bikes? (I shall never call them steep head tube angled small front wheeled bike agin) was it purely for aerodynamics??

The TT frames of the day were about the same price of the road equivalent from a bespoke builder, indeed the road frame was probably a better bargain as it had more braze ons LOL. I'll have a look at my Cycling mags as there is an advert which includes Martyn Pynes frame (ish).

The Low Profile bikes had to come about as "aero" became more prevalent as it reduces frontal area, have a google for Alf Engers "Speed Machine" as that's probably the apex of basically non aero technology..........

Road bikes followed the ultra short wheelbase for a while probably culminating in the 75/75 Holdsworth Pro frames of about 1976 which were quietly dropped as they were a bit of a nuisance in a bunch ! My avatar has me on my Falcon Team bike which should be 74/73 The MKM ultimate was another SWB design where big footed people kicked the rear mech LOL, rather like the angled cranks

I find 70's TT bikes fascinating as I used to race them but were a revolutionary dead end as we didn't think about aerodynamics much and we could lose more weight going to the toilet before a race than by fitting SABA replacement titanium seat bolts.

Shaun

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Nob":3kml8gox said:

Click to expand...

OMG! :shock:

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Yeah your eye don't need any practice to spot that one! It's almost like a caricature of a TT bike. One of your old steeds, Nob? Please tell us you didn't use any of those gears to cycle up that hill...