Size Advice

richjturner

Hi, was looking for a new aero bike and came across a De Rosa SK 54cm frame with 50% off on Wiggle. It ticks all the boxes, but I'm not certain of sizing - I can't make sense of size charts. I took a punt as can easily send it back if needs be (though I don't want to because it's beautiful!).

The De Rosa geommetry is here:

http://www.derosanews.com/wp-content/up ... farina.pdf

and my current bike, a Colnago CLX 3 2013 size 50cm is here:

https://www.sigmasports.com/item/Colnag ... metry/388K

Can anyone tell me if I've bought the right size? According to the size charts on Chain Reaction I have but...

Thanks!


Rich

Bottom briquettes

The De Rosa has an effective top tube length which is 13 mm longer than your current bike. It’s not that much bigger, and I reckon you could easily adjust it to get the fit right.

richjturner

Bottom briquettes wrote:

The De Rosa has an effective top tube length which is 13 mm longer than your current bike. It’s not that much bigger, and I reckon you could easily adjust it to get the fit right.

Is that enough of a measure? I should also say that on my Colnago I have quite a short stem - 90mm. If I apply the same to the DR where would I be able to shrink without impacting the ride? I'd like to keep it, but not at the expense of handling.

Cheers,

Rich

First.Aspect

Anything less than a 90mm stem starts to feel a bit odd, at least in my experience. I think I had to use a 70 or 80 back when I was a student, and the only 2nd hand bike I could get was at least 2cm too long in the tt. You can get used to it, but why would you?

The only other ways to claw back some of the reach is either find some bars that place the hoods closer to you (there can be around 10mm difference between brands) or by moving the seat forward a bit.

Does the Colnago have a straight or lay back seat post? Where is the clamp wrt to saddle rails? I'd say if you have an in line post on the Colnago already, and the saddle clamped anywhere in the middle of the rails, the DeRosa will be too big for you.

If not, the next step will be the post that comes in the DeRosa. Is that straight or lay back, or do you have the choice?

arlowood

richjturner wrote:

Bottom briquettes wrote:

The De Rosa has an effective top tube length which is 13 mm longer than your current bike. It’s not that much bigger, and I reckon you could easily adjust it to get the fit right.

Is that enough of a measure? I should also say that on my Colnago I have quite a short stem - 90mm. If I apply the same to the DR where would I be able to shrink without impacting the ride? I'd like to keep it, but not at the expense of handling.

Cheers,

Rich

To get the same position for your bars on the De Rosa relative to your Colnago you will have to fit an 80mm stem (actually 77mm is the difference but I don't imagine they make that size stem).

It could work out OK but the shorter the stem you run the more twitchy the handling is likely to be. Problem is there's no way you can know if it will work until you build up the frame and ride it. By that time it will be too late to send it back.

Any amount of pontificating by contributors to your thread won't answer that final handling question so really you have to decide if you want to take the risk or not

richjturner

First Aspect wrote:

Anything less than a 90mm stem starts to feel a bit odd, at least in my experience. I think I had to use a 70 or 80 back when I was a student, and the only 2nd hand bike I could get was at least 2cm too long in the tt. You can get used to it, but why would you?

The only other ways to claw back some of the reach is either find some bars that place the hoods closer to you (there can be around 10mm difference between brands) or by moving the seat forward a bit.

Does the Colnago have a straight or lay back seat post? Where is the clamp wrt to saddle rails? I'd say if you have an in line post on the Colnago already, and the saddle clamped anywhere in the middle of the rails, the DeRosa will be too big for you.

If not, the next step will be the post that comes in the DeRosa. Is that straight or lay back, or do you have the choice?

Thanks for the reply. I don;t want to shorten further than 90mm - if it comes to that I'll return it. It's too much money to spend if it;s not right. Here's a pic of the Colnago:

https://www.racycles.com/product/detail/1571

and the De Rosa:

http://www.wiggle.co.uk/de-rosa-sk-disc ... road-bike/

Both with the original bespoke seat posts.

Thing I can't get my head around is the overall position. Seat tube and top tube lengths don't paint the whole picture.

Cheers,

Rich

richjturner

arlowood wrote:

richjturner wrote:

Bottom briquettes wrote:

The De Rosa has an effective top tube length which is 13 mm longer than your current bike. It’s not that much bigger, and I reckon you could easily adjust it to get the fit right.

Is that enough of a measure? I should also say that on my Colnago I have quite a short stem - 90mm. If I apply the same to the DR where would I be able to shrink without impacting the ride? I'd like to keep it, but not at the expense of handling.

Cheers,

Rich

To get the same position for your bars on the De Rosa relative to your Colnago you will have to fit an 80mm stem (actually 77mm is the difference but I don't imagine they make that size stem).

It could work out OK but the shorter the stem you run the more twitchy the handling is likely to be. Problem is there's no way you can know if it will work until you build up the frame and ride it. By that time it will be too late to send it back.

Any amount of pontificating by contributors to your thread won't answer that final handling question so really you have to decide if you want to take the risk or not

Yeah, seems fair. I have asked my LBS as well - I had a bike fit last week so am hoping they can give me a more conclusive answer (or best guess!). If I could find one in stock somewhere it would help so I could at least sit on it... might try that.

First.Aspect

At the risk of pontificating, as the other very helpful chap said, my hunch is it's too big for you. They both look like they have about the same seat post set back. Roughly.

The 50 cm Colnago has a steep 74 seat tube angle. The de rosas is more like 73.5. This puts your saddle slightly further behind the bb, all things being even. Combined with a 13mm longer top tube, both you feet and your hands are going to be further in front of your bum on the de Rosa, which will tighten your hip angle noticeably.

richjturner

First Aspect wrote:

At the risk of pontificating, as the other very helpful chap said, my hunch is it's too big for you. They both look like they have about the same seat post set back. Roughly.

The 50 cm Colnago has a steep 74 seat tube angle. The de rosas is more like 73.5. This puts your saddle slightly further behind the bb, all things being even. Combined with a 13mm longer top tube, both you feet and your hands are going to be further in front of your bum on the de Rosa, which will tighten your hip angle noticeably.

Thanks for reply. I think (may be wrong) that the saddle sits slightly forward on the DR seat tube compared to the Colnago, plus I do have a little room to move my seat forward, so it would give me a some room to play with. However the top tube still remains longer so I'm starting to think it's not going to work. My Colnago is pretty much perfect following a bike fit, so I don't want to mess with it. Still waiting for my LBS who did the fit to confirm, but have to agree that it's looking too big. I can get the frame in a 52 at the same price but it's the non disc version and I think I want discs... hmmm.


R

w00dster

I'm presuming you are looking at the full bike and not just the frame?
Going slightly off topic so feel free it ignore. But would the below be in budget and an option?

https://www.canyon.com/en-gb/road/aeroa ... 0-di2.html

Do you have Aero wheels to go with the De Rosa already or would you be buying a set of aero wheels? (The wheels will be a significant part of the aero package and an aero frame without deep wheels is just wrong!)
The reason I linked the Canyon is that it is the full aero bike with discs for just over £4k, so aero wheels, aero cockpit, aero frame and ultegra DI2. It may be a good few years old new, but I just can't see how the frame itself will be significantly slower than for example, the new Madone (same spec is £7.2k) or the Cannondale System Six (£6.5k).

I have the rim brake version on order. I was lucky enough to be able to test ride one before I ordered so was very happy with the bike. I've ridden a fair few top end race bikes and I'm more than happy with it for the price I paid (£3200 for my Ultegra Di2 Aeroad)
I was tempted by the System Six and the Madone, but couldn't justify the additional spend for what is in all likelihood going to be about 5 watts difference at the most. (There's likely to be a new Aeroad coming out hence the sale)

cld531c

Can you not order it, sit on it and compare it to the Colnago and if its too big send it back?

richjturner

So the good news is a 52 came into stock so I snapped it up. Will return the 54. Much as I wanted it to fit the consensus was that it was too big and that was my hunch as well. It's on its way

richjturner

w00dster wrote:

I'm presuming you are looking at the full bike and not just the frame?
Going slightly off topic so feel free it ignore. But would the below be in budget and an option?

https://www.canyon.com/en-gb/road/aeroa ... 0-di2.html

Do you have Aero wheels to go with the De Rosa already or would you be buying a set of aero wheels? (The wheels will be a significant part of the aero package and an aero frame without deep wheels is just wrong!)
The reason I linked the Canyon is that it is the full aero bike with discs for just over £4k, so aero wheels, aero cockpit, aero frame and ultegra DI2. It may be a good few years old new, but I just can't see how the frame itself will be significantly slower than for example, the new Madone (same spec is £7.2k) or the Cannondale System Six (£6.5k).

I have the rim brake version on order. I was lucky enough to be able to test ride one before I ordered so was very happy with the bike. I've ridden a fair few top end race bikes and I'm more than happy with it for the price I paid (£3200 for my Ultegra Di2 Aeroad)
I was tempted by the System Six and the Madone, but couldn't justify the additional spend for what is in all likelihood going to be about 5 watts difference at the most. (There's likely to be a new Aeroad coming out hence the sale)

I did look at the Aeroad but I'd be a small and it hasn't been in stock. I only need a frame really - have almost new Di2 group on my other bike, though need to swap the brakes and levers for disc version. With the frame at half price it should work out comparable once I've added wheels and cockpit.

StillGoing

I use an 80mm stem on my Reacto and find no problems with it. A longer stem is better for quick tight turns supposedly.