Bike fits & frame finder services

I’m looking to buy a tri bike for my second IM but, having worked out what I’ve spent on triathlon since starting out three years ago, I’m slightly horrified and don’t want to spend another small fortune.

I’m aiming for a sub-10 time with a sub-5.30 bike split so need decent aerodynamics. eBay suggests I could get a second hand entry-level tri bike for about £500, and I’d rent decent wheels for the race.

I’ve looked at getting a tri fit with aerobars on my road bike but it has disc brakes so it seems impossible to rent race wheels, or buy them without spending more than I would on a tri bike.

Fit is obviously important and Edinburgh Bike Fitting’s frame finder service has been recommended to me, as well as a tri fit once I’ve got the bike. However at almost £200 each these two services together would cost almost as much as the bike itself.

My questions are:

  • Has anyone used a ‘frame finder’ service and are they worth it? Or can you rely on size guides from bike manufacturers?
  • For someone with three years’ experience with bikes and triathlon is it a stupid idea to try and do a bike fit myself with my trainer and a mirror?!

Any help would be much appreciated.

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check out - supply ex-demo and refurbed TT bikes so maybe have something that matches what you want. not used them myself but came across them recently and looks interesting.

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IMO, you’re looking at the problem the wrong way round. Think of the fit as the essential spend and the bike as the secondary spend. The right fit from the right person will give you more time savings rather than shoehorning a cheap 2nd hand bargain to fit you.

The fitter should be able to give you some options, that you can then go and scour the 2nd hand market for.

Just my 2c


Whilst I agree with the principles FamPom is suggesting, I can see the OP’s point if you aren’t spending a lot of money on the bike. 100% go through that kind of process if you are dropping thousands on a super bike, but if you just want to get something basic and cheap, then you kind of become reliant on just getting something that roughly works and is in budget.

Given the time of year, the OP also needs to get something fairly quickly assuming they are racing this year.

To the OP, it’s certainly not unrealistic to deliver those kind of times (see @Chriswim who road a great time with an adapted road bike I believe), but in my opinion, the benefit of a TT bike is something that fits you well such that you can hold the aero position for 99% of that intended bike split time. Shoe-horning yourself onto something kind of defeats the point. And you need time to acclimatise to the position, hence needing something pretty soon if the race is this year. I have crappy power, but rode a 5:18 simply because I stayed aero for everything bar corners and refilling bottles.

Personally, all my money got spent on my TT bike, and I still have a crappy road bike. Prior to that, I got a cheap TT bike for £500 off one of our club coaches, but it cost me nearly that again to change a whole load of components to actually make it properly comfortable. And it still wasnt great. Hence replacing within about 12 months. It did at least make me confident I did want to spend the money on something better. But I’d have not wanted to do 180k on it (I just did 70.3’s)


Yes… because there is an excellent App, Bikefastfit, that will do a much better job for a very small investment (I think it is about £9.99)

Of course it is not as good as a proper bike fit, however, it is much better than nothing. Before I had a bike fit, I used the app, when I actually had a bike fit, it was pretty much spot on… however, there are many other benefits of a bike fit, such as looking at technique, identifying areas that you can improve, etc.

A good used TT bike will be 99% as fast as a brand new one. Depending on what course you are doing, Di2 can be a real benefit, as you can change gear on aerobars and on base bar. For a hilly or windy course, this is a big benefit. For a flatter course, won’t make much difference as you will be in aero position most of the time.

Now that many people are upgrading to disc brake TT bikes, they are selling off old TT bikes and most importantly wheels, so some great used bargains around. Pretty often a TT bike doesn’t get used much, so wear shouldn’t be an issue. Something like a used Cervelo P3 from 2012/13 could be in your price range. However, I would go with a top spec older bike rather than a lower spec new one

If you are looking at sub 10 hrs, you really need to be looking at close to 5hrs on bike, unless you are a spectacular swimmer or runner - 1:10 swim, 5:10 bike, 3:30 run, 10mins transition

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This was my first thought! I have been so close to Sub-10 several times, and it was my bike that just wasn’t strong enough (normally 5:2*)

I wouldn’t be using me as a good example of bike fit :joy: more that last years IMUK course meant road bike didn’t hamper me as much. It was a good time for the course, but still over 6 hours bike split.

Shhh, he’ll start bidding on the P2 I’m watching :wink:

I’ve never had a professional fit but used an online calculator from Competitive Cyclist which does road, MTB & Tri fits to get a starting point which I then tweaked over a period of time.
I’ve just tried to go into it and it now says it’s not available outside the USA due to GDPR but you could probably get round that with a proxy server if so inclined.
Ps. I threw myself to the ST wolves by posting a “Critique my fit” post on there, expecting to get mullered and, apart from my head sticking up like a Meerkat, got pretty positive feedback.

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Edinburgh Bike seems to use the Retul fit data base. I was thinking about this and there are 2 things you should consider.

  1. the actual bike fit
  2. being aero on the bike.
    The fitting numbers might look great re stack and pad height but you might be as aero as a parked bus.
    There is a lot of homework you can do by knowing what your measurements are and then looking at bikes and frames on the manufacturers sites. Also asking the great members of TT can be a source of advice especially on tidying your garden or garage.

You might be able to get aero and look perfect… but can you hold that position for 5+ hours on varied terrain? :thinking:That’s what a bike fitter makes sure of. There’s a lot more to it than just a few dots on shoulder, elbows, knees and ankles.

And for that same reason, talk to a person rather than a database to find the right bike


Thanks everyone for the help.

For a five-hour bike split the consensus seems to be:

  1. Buy a used, higher spec older bike and wheels

  2. Get a bike fit in order to maintain an aerodynamic position for the whole bike leg

I’ll save up and be patient bike-hunting - I’ve decided Chester marathon in October will be my focus this year which gives me time. I’ve been away travelling and start a new job in April so can’t prioritise or afford IM this year unfortunately!


Seems sensible to me. You’ll have a nice big running base going into the winter. Keep that ticking over and ramp up the bike training on the turbo through the cold dark months and you’ll be in a good position come spring.


A sub 5 bike split is a true milestone in Ironman racing. Best of luck :+1:t2:


@GGG are you located near Edinburgh based on the comments for Edinburgh Bike Fit? If you haven’t considered it already have a chat with the local TT clubs. I learnt as much from the guys at the TTs as I did anywhere else for being aero.

@awildt I agree with you. I was Retul fitted by Freespeed when I broke my shoulder and I needed to be fitted in a way that would keep me in the aero position for Roth. Once comfy I could then start to tweak to make the position more aero.
I picked my last TT frame from talking to plenty of TT’er and going into the stores to see the frames once I had a grasp of what was out there from forums and checking the specs online. I can hold my own on a TT bike with a 54min 25 and a 1 hour 56 min 50.

Yes I’ll be in Edinburgh from April, will look the the local TT clubs.

I’d like to give time trialling a go - the beauty of triathlon to me is that it has opened up endless athletic things to do, it’s just a matter of fitting it all in!

Looking for similar advice, on how to know what size TT bike to buy second hand. Asked a local fitter if he could give advice if I came in for pre-sale measurements, he offers this service for road bikes, but not for TT bikes, and his advice was that so long as you’re close enough, that he’d be able to fit it so long as the bike has everything to adjust the front end to match.

He was saying there are necessary things that would be sold with a bike when new that enable this adaptability that tend to get lose in second hand sales. I’ll admit I got a bit lost, assuming he’d just need allan keys +/- different stem/put in some spacers that he’d be able to provide if needed to increase the height? And what is a shim?

Keep hearing that a good fit is by far the most important thing, so I want to pick a bike based on whatever is going to fit best, and have no idea what I’m looking for. Are there some bikes that are non-adjustable, or things I should be asking for in the sale?

I think you might need to actually pay for a TT fit rather than “chatting to a fitter for some advice”. This will give you the key measurements. Then if the bike fitter is good (key point here that you need to decide) they should know the TT market and identify which brands are more likely to work. This should narrow it down for you.

Many 2nd hand TT’s are sold with a cut fork or fixed seat post or integrated bar and stem so those would all cause a headache for adjustments.

Online they advertise a service of pre-fit measurements to give advice for which size bikes to buy so that’s what I rang to book, but turns out that’s only for road bikes.
Was while we were on the phone he was trying to explain why it wasn’t as crucial for TT bikes :thinking:

I am by far an expert. But I’d have thought the opposite would’ve been true? :man_shrugging:

On a TT bike, especially for a tri, you’re going to be locked into the same position for hours on end and then expect to run after. Surely a bad position is going to build, build, build problems? But on a road bike you’re up out the saddle, on the hoods, drops base bar etc etc.

But I know nothing. So this may well be nonsense. :joy:

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