TT bike sizing?

JesseD

Thinking of buying a TT bike or frame set but have no idea on how to size one?

Know exactly what will fit me with road bikes but the world of TT bikes and bike fit is completely new to me, anyone offer any advice or links to good bike fit sites for TT bikes?

For reference on a road bike I look for a stack height of 565mm - 570mm and a reach of no more then 396mm.

Thanks all

napoleond

There's no one rule. As I've found to my expense.
You need to try some. A good starting point is a reach 2cm shorter than your road bike.

simon_masterson

^ what Nap said - when I put my first TT setup together, I just found some guideline numbers and bought a frame. Do you have any idea what position you're going for?

JesseD

Don't want to go super aggressive as I don't think my lower back will be able to handle it? But I have seen those bars with the high spacers under the extensions which it think would solve that problem, then as I get more flexible I can remove some spacers etc.

It's the reach that confuses me as I don't want to go too long in the TT. I have been offered an Argon 18 TT frame set by a mate which has a 53.5 top tube, can't try it as its stripped down already.

It may be worth a punt as its cheap.

Anonymous

My road bikes frame size is 53cm (Bianchi Sempre Pro, Via Nirone & Oltre XR1)

My TT/Tri bike is XXS (47cm) Scott Plasma Mk 2

The Stack height is nearly identical and the top tubes are very close in length. I would really make sure you sit on one before you buy. Some people say a TT frame is a size down from your regular frame but if I had done that it would have been way to big for me.

mfin

What size is the Argon 18 TT Frame (S/M/L)?
What size, make and model is your current road bike? (and stem length, amount of spacers under stem, and how tall is its headset conical top cap?)

It is likely from this information that it would at least be able to see if there are any alarm bells about the Argon18 for you.

JesseD

Current bike has a stack height of 580mm and a reach of 386mm with a slammed (zero spacers) 110mm stem +/-6 degrees, but I now find it a tad too high so my next road bike will be lower at the front. It's a 56cm Felt Z75.

Argon I think is a small with a 53.5cm top tube.

mfin

JesseD wrote:

Current bike has a stack height of 580mm and a reach of 386mm with a slammed (zero spacers) 110mm stem +/-6 degrees, but I now find it a tad too high so my next road bike will be lower at the front. It's a 56cm Felt Z75.

Argon I think is a small with a 53.5cm top tube.

Sorry, the bike you are getting those Reach and Stack values for is a 56cm Felt Z75, is that what you are saying?
That's not what the numbers say in the geom table on here http://www.wiggle.co.uk/felt-z75-disc-2016/ ...maybe yours is a different year though? Or is it this one in 56cm?

Don't worry about the Stack and Height, Stack and Height aren't needed.

I'm guessing if you are on that bike in that geom table with that stem etc that you are about 6ft0" ??

I've actually ridden a small E112 Argon18 by the way, so just trying to get more of a picture.

JesseD

Mine is a 2015 bike, this one:

http://www.wiggle.co.uk/felt-z75-2015/

The argon 18 is a small I believe, my mate who is selling is on holiday for 2 weeks so I will double check when he gets back.

What were your impressions on the E112? The one he's selling is an E114, it's a 2010 one I believe but in great condition, and if it fits will be an inexpensive way for me to try TTing and see if I get on with it or just stick to road racing

mfin

JesseD wrote:

Mine is a 2015 bike, this one:

http://www.wiggle.co.uk/felt-z75-2015/

The argon 18 is a small I believe, my mate who is selling is on holiday for 2 weeks so I will double check when he gets back.

What were your impressions on the E112? The one he's selling is an E114, it's a 2010 one I believe but in great condition, and if it fits will be an inexpensive way for me to try TTing and see if I get on with it or just stick to road racing

Gotcha, geom table seems right on that one for the stack/reach you said.

So, you say your next bike will be a bit shorter head tube (how much lower would you want to be, 1cm?), was I right that you are about 6ft dead?

What saddle height do you have on the road bike from centre of BB to saddle top?

The one I rode was about that year too, obviously the 112 not the 114. Good bike, very stiff, great power transfer, heavier than some carbon TT bikes but that should not be considered a disadvantage. It's a capable TT bike.

I'm asking for more info on your height and saddle height to know a bit more because at the moment I am thinking the Argon would be much better in a Medium really.

(By the way, I'm 6ft dead, and if I had your Z75 I'd want it lower at the front than it would go and I'd be riding it with an 11 stem as well... so I'm trying to form a picture, as the small Argon would have been too small for me, too low at the front, and too short).

JesseD

I'm just under at 5ft 11, saddle height is 775mm from middle of BB to top of saddle.

On the road bike the reach seems perfect but I am too high now as I have lost weight and got fitter, so am thinking a 1cm drop would be achievable maybe more with some flexibility exercises.

mfin

Ok, you are an inch shorter than me and my saddle height is 755mm (but I am quite short in the leg for my height). Looks like you have a bit longer reach than me too, but arm lengths and flexibility come into it too.

Seeing as you have a just a touch more reach than me on your Z75, the shortness of the small argon might come into play more for you, as will the fact the saddle to bar drop would be more for you with your longer legs. Can you see where I'm coming from in thinking the small will be too short and low still?

I couldn't have made it work, so I ended up on a Medium Canyon Speedmax AL which was great, like a glove and it had enough potential to go lower at the front too. I ran that with a -17 120mm stem on 3T Aura bars, with one 10mm spacer.

Here's its geom bottom of post below: (see it is only about 10mm longer but it is taller at the front than the small Argon I believe ...by the time you have that Argon higher spaced at the front to be equivalent, and higher again if you want less drop as your saddle is higher than mine by 20mm on your road bike you'd need more stem length again maybe)

I don't know if any of this is helping you at all!! My saddle to bar drops are not the most (so low bikes like Supersix Evos wouldn't work for me), but I am flexible enough that the Z75 is too 'sportive' and high at the front for me to get to fit.

Note... the e114 in small has a 9.5cm HT and can be increased to 10.9 or 11.9 with those headtube extenders, so if you run it will all of them it is getting close to the bike I chose but is still a bit shorter. If you run a fair bit of layback and are quite long in the thigh you MIGHT get that small to work, but if that sentence doesn't apply to you the chances are lessened.

JesseD

mfin – thanks for all your help and advice, I think it kind of makes sense.

Am I right in thinking that you have a proportionally long body compared to your legs? Would that contribute to the longer top tube?

I don’t have overly long legs or arms however the position on the felt is very comfortable, although too high at the front for racing which is why I want to drop it 10-20mm bringing the stack height down to around the 560mm-570mm range, reach is perfect pretty much although as I go down in stack I may need to lengthen the stem by 10mm (trial and error here).

I did have a while ago a Planet X Stealth Pro Carbon when I was doing triathlon (I know I know!!), that had a 530mm top tube with a 110mm stem and a 100mm head tube, reach was ok if not a little long but I did find the saddle to bar drop a little extreme, that said the PX bars that came with it were pretty low so I couldn’t ride in the pads for long (maybe being a bit overweight and not very flexible were the main issue?).

mfin

JesseD wrote:

mfin – thanks for all your help and advice, I think it kind of makes sense.

Am I right in thinking that you have a proportionally long body compared to your legs? Would that contribute to the longer top tube?

I don’t have overly long legs or arms however the position on the felt is very comfortable, although too high at the front for racing which is why I want to drop it 10-20mm bringing the stack height down to around the 560mm-570mm range, reach is perfect pretty much although as I go down in stack I may need to lengthen the stem by 10mm (trial and error here).

I did have a while ago a Planet X Stealth Pro Carbon when I was doing triathlon (I know I know!!), that had a 530mm top tube with a 110mm stem and a 100mm head tube, reach was ok if not a little long but I did find the saddle to bar drop a little extreme, that said the PX bars that came with it were pretty low so I couldn’t ride in the pads for long (maybe being a bit overweight and not very flexible were the main issue?).

Yeah, I have a proportionally longer body, and am a touch taller, so in theory if arms were left out of it, I would be happier on a longer top tube than you, make sense? But, counterintuitively to that I am running a slightly shorter reach than you, about 1 cm less, so the A18 in Small you'd think would favour me over you, especially as my saddle height is lower so the low front on the A18 is less of an issue for me.

Anyway... remember this is all entirely speculative. I think there are a few people at 5'11" who would choose the small A18 over a medium one, but not too many. I know it would be a waste of time me buying one in that size.

Ah... now you mention the Planet X, so you do have some experience. You need to remember if you are building up a frame you have a lot of different bar setups you can buy too.

Is there any way you can get to sit on or ride a few TT bikes?

Also, remember you could ask on the TimeTriallingForum as well.

JesseD

I wouldn’t call it experience as such, plus it was over 7 years ago now, I bought the PX complete and changed nothing, rode it about 10 times maximum and that was it. This time round I am going to build the bike up so I know I can change things like stem length, add spacers under the stem, get different bars which will help with saddle to bar drop etc, the hard part is getting the right frame size.

What I may do it try out a couple of club mates bikes in different sizes and see how they feel and what the geometries are like and go from there, I think the argon still has the saddle and bars on it so I may see if I can chuck some wheels on to get an idea of how it feels.

Sizing road bikes are easy, TT bikes seem to be some form of dark art!

napoleond

A medium Planet X Exocet 2 sounds about right for you.