So, I’m kind of between sizes. Obviously is varies between brands but between a 51/53 or 52/54 or small/medium.

Looking more closely at these though, while there is a good size worth of difference in the effective top tube length, a lot of this is due to the seat tube angle.

When you look at the reach, it can be as little as 3mm between those two sizes. So, I’d be interesting in your thoughts as to whether to size up or down.

One thing tempting me to size down is that I like 170mm cranks which are more common on the smaller bike and often go up to 172.5 on the next size up. Doesn’t sound like much but from past experience, yes it is enough to cause my sensitive knees to complain.

Having said that, the cost of a chainset isn’t reason enough to buy the wrong (maybe) sized bike.

So, your thought please.

Sit on them both and see which fits best – you spend a lot of time sat down on a road bike and need to be comfortable.

I have a 54cm Spesh and a 52cm Pinnacle. I know I haven’t helped one jot….

That’s the thing, sitting on them, I can’t tell 3mm difference. I’m not sure I’d know on a ride around the block. Would I know after 6 hours in the saddle? probably, but it’s too late by then.

Plus, it seems near impossible to find a shop that does test rides with both sizes in stock!

You’re unlikely to hate one and love the other.

You do seem to overthink things.

So what the difference between a 54 and a 52 with a longer stem and more post showing? serious question, how would it affect the ride, would it make a difference. I ask as I’m in a similar position and I was planning to size down and just buy a longer stem. Think it looks better as well.

double post

I’d be considering the differences in head tube length between the two frames as well.

Most size charts recommend a 52cm for my height, but I ride a 54cm purely to get a higher front end.

don’t just go on height!

so many people make this mistake.

Take a book, shove it as far into your crotch as possible and measure from the top of the book to the floor.

If you are say 5’6″ with a 30″ inseam, you wont need to worry as much about head tube length as someone the same height but with a 32″ inseam (me).

I’d always compare EVERY dimension with your curernt bike.

You’re right Al, I do. Believe it or not though, it’s part of the enjoyment for me. All the planning, questioning and analysis.

Go down a size and add a longer stem. This puts more weight over the front wheel and feels more stable cornering. You may need (more) spacers for the handlebars as the head tube will be 1-2 cm shorter. I ride a Medium Giant Defy (54.5 cm TT), but at 179cm, can ride a M/L as well. I also ride a Medium TCR (55.5 cm TT) and a 56 cm Kona (56.5 cm TT). The stems are 115, 100 and 90 cm to accomodate geometry, and if I’m honest, the Kona is really a size too big.

FWIW, a half degree head and seat tube angle is worth a centimetre in top tube – factor that into the equation. For road bikes, you won’t notice the handling difference between 72.5 and 73 degrees (all other things being equal). Seat tube angle doesn;t really matter because saddle rails are so long you can position yourself in the same relative position over the BB for about 3 degrees of difference.

all of the above is well and good unless he’s knocking out centuries where more weight over the front end is great until he hits 50 miles and his back aches! (again, if he has long legs)

also with the smaller frame longer stem theory, that can sometimes put your pedalling dynamics out massively which can affect power output and climbing comfort

I’m mulling over basically the same thing – whether to go for a 53 bianchi or a 54 cannondale. The 53 felt a bit small but faster to turn and corner on and I could put a longer stem on it. I’m guessing it would be harder to adjust the 54 to feel smaller

I am intending on doing long rides at a firm pace rather than an hour’s blast. Need to be able to fun afterwards as well.

I was in a similar position a couple of years ago 56 too short, 58 too long. Then a friend spotted a Bianchi in the sale so I went to try it and they have odd sizes and 57cm fitted me perfectly, so maybe a possible solution is look at brands like Bianchi which do odd sizes.

I hate to say it but odd numbers mean nothing at all.
Just because the bianchi was a 57cm doesn’t actually mean it was either bigger or smaller than the other bikes you mentioned.

Just look at cube for instance, their 56cm is most people’s 54.

also with the smaller frame longer stem theory, that can sometimes put your pedalling dynamics out massively which can affect power output and climbing comfort

Please explain how? And why would one’s back ache any more – as I said, the relative positions of the three contact points are all in the same position for all three of my bikes that are three different sizes. That is the point of changing stem length and adding spacers. All that changes is that the centre of gravity is 0.5-1cm further forward between the wheel contact points for the smaller frame. That does improve handling downhill (e.g. reduce shimmy), but you won’t notice it climbing.

Smaller frames can also have a shorter wheelbase, but there is much variability, more between makes than within them. Anything under a metre will feel racy.

53 bianchi or a 54 cannondale

Cannondales seem to come up pretty large due to the parallel geometry. We have a 54 cm, which with the standard 100 mm stem fits me fine as well.

Thanks TiRed, that’s really helpful. I’m used to a 54 cannondale but it has always been a bit of a long reach for me and is pretty aggressive position particularly on the drops. When I first got on the 53 I did once hit the bar with my knee, but that may have just been me not being used to it. I do worry a bit though – is it better to be nearer the front wheel for climbing?

Fit isn’t really about “getting used to it”. The most common problem I see is bars too far away, and too low. Our CAAD8 has a long steerer tube and the bars are “slammed”. The saddle to top of bar drop is the same 8cm as all my bikes. This drop is entirely personal. You could start with this and go up or down as you get used to the position. I’ve gone down to 10cm but always seem to come back to 8cm. In days of old, bars were much higher and the drop smaller. But the curve on the handlebars much deeper so riders would not ride on the hoods as much. Modern bikes have shorter headtubes and pros ride on the hoods more. We mortals put the bars back up by flipping the stem (ugly) or spacers (less ugly) or buying a “comfort” geometry bike like the Synapse. Modern drop bars have less of a drop to “compensate” for the lower handlebars. This can mean that there is not enough clearance when sprinting out of the saddle on the drops.

There is no magic. Find the saddle height and fore aft that suits you first. Then set the bar reach (stem length) and height. To set reach. Lean forward on the hoods and the angle at the elbow should be 90-100 degrees. I’ll bet your angle is bigger. The usual symptom is a pain in the neck after a couple of hours in the saddle due to hunching of the shoulders.

For climbing some might suggest being further back is helpful. Out of the saddle, it really won’t matter. In the saddle, I’ve not founf much difference, but of the three bikes, the nice ultralightweight carbon Defy always climbs the fastest 😉 regardless of geometry.

Just get the basic three contact point triangle right and set any bike accordingly.
For me;
Saddle top to BB is 74cm
Tip of Arione saddle is 5cm behind BB
Drop from saddle to top of bars 8cm
Tip of saddle to bars is 54.5cm

All my bikes are the same. Including my SS mtb, although the bars are higher.

I would always size down not up. Nothing worse than trying to make a bike that is too big fit. Chances are you may have to put a longer stem on and if anything that will make the bike more stable. Short stems just get too twitchy. Also aero position will be far better

all i’m saying is that i’ve seen a lot of guys try to emulate pro’s with a tiny frame and a longer 120mm + stem.

This tends to put their weight over the bar which is great for sprints and handling but not so for sportives or climbing.

i would also disagree with ‘sizing down’ – get the bike that is the correct size in the first place.

I’ve found that a 50mm drop is suitable for most and anything further (i’m dealing with all ages, abilities and levels of flexability) tends to put more strain on neck and shoulder muscles.

50mm drop on a road bike isn’t very much at all.
It is very easy to get set up on a bike with twice that and be able to ride all day in comfort
Hood positioning, bar rotation, seat height, fore aft position of seat, cleat positioning and importantly reach are all big factors.
The question was about which way to go-obviously get the right size but if you have to go one way or another go down.

The question was about which way to go-obviously get the right size but if you have to go one way or another go down.

Completely agree. I was between sizes for the Defy and with an integrated (read cut) seatpost, there was no returning it after deciding it might not be the right size.

Anything longer than 120mm and you are i) a pro or ii) a poser or (more likely) iii) riding a bike that is too small. My vintage track bike is a 19″ frame and far too small, so it has a 120mm stem. But it is old and 531c and I bought it used and cheap for fun.

Not all 52/54 size road bikes feel the same anyway. I swung my leg over at least a dozen different bikes before I found one which “just felt right” size wise

.

I’ve found that a 50mm drop is suitable for most and anything further (i’m dealing with all ages, abilities and levels of flexability) tends to put more strain on neck and shoulder muscles.

That’s a strange post, it must surely depend on the individual? Ive just measured my drop and it’s somewhere between 120mm and 130mm. TiReds is 80mm, which is again, more than 50mm.

The important measurements for the op are reach and stack.

I think genrally in terms of handling, weight distriubtion etc. a longer stem is preferable. Which means it’s better to size down. But if you end up having to run 40mm of spacers then perhaps consider a different frame.

Also, dont get to worried about a centimeter or a degree here or there, there’s loads of adjustment in saddles/seatposts/bars/stems

The important measurements for the op are reach and stack

Depends :-). It could be effective top tube and ideal stem length. Whatever it is it’s all about knowing your ideal frame dimensions and being able to instantly look at a bikes geometry chart and know which one fits you (if you are mentioning reach and stack then you probably know this but the OP doesn’t )
The given frame size is meaningless as is anecdotal internet sizing statements that start with “I’m x. ft and ride an x”

If you know the 2key measurements (whatever they are) and how head tube length/stem length can change that then you know which frame size you want. Agree about the stem length being better longer and sizing down.

you run a 130mm drop from the top of the saddle to the top of your bars?

That seems extreme to me.

There are variables like arm length but many of the people complaining about their position are better off for a lesser drop from one to another.

Frame size, it’s not about the height, despite that being the measurement number. And beware of online guides.

I am a slightly odd shape – I have medium to short legs, and short arms for by body shape. If I buy a suit, it will be short in the hjacket but I might need regular legs.

Online suggests at 5’7 I should be riding a 53 cm bike. When I tried a couple of 53’s, they were so long in the top tube, that I was at full stretch to just grip the hoods, it was unrideable.

In the end, I bought a Bianchi, which is apparently measured up at 50cm, and its compactly perfect for me, despite apparently being suitable for people several inches shorter. The issue wasn;t the seat height, that was not much different, but the reach.

I hate to say it but odd numbers mean nothing at all.
Just because the bianchi was a 57cm doesn’t actually mean it was either bigger or smaller than the other bikes you mentioned.
Just look at cube for instance, their 56cm is most people’s 54.

Not all 52/54 size road bikes feel the same anyway. I swung my leg over at least a dozen different bikes before I found one which “just felt right” size wise

this + Tireds post about personal measurements.

I initially borrowed a 55cm Bianchi and then bought a 54cm Orbea (with same top tube length). Ive subsequently bought a 52cm Lapierre which has the same virtual TT (ie. measured horizontally from head tube) as the Orbea, but a 10mm longer effective top tube/reach due to the higher (and further back thanks to seat tube angle) saddle.

I measured and recorded all the dimensions Tired listed off my Orbea, and set my Lapierre up to be the same. As Ive adapted to road riding Ive taken advantage of the extra length of the Lapierre (now using same length stem as the Orbea) and have dropped the bars a little.