What size bike do I need?

[Kamil1308]

I am trying to buy my first road bike but have no idea about sizing. Everyone I ask has a different opinion. The people in my bike store seem to have no clue or instrest. All the bike fitting companies only do a fitting for bike you already own so that's no help if I don't have one.

I am 5'10 and my leg in seam 32".

TIA

[thelawnet]

I don't think it matters THAT much, unless you have had problems in the past.

I am 6'0" and have had 'M' and 'L' frames and am quite happy with either.

I would be looking at an M in your case although different manufacturers vary, but generally if you have a choice between two sizes probably go for the smaller one.

[horizon]

I am trying to buy my first road bike but have no idea about sizing. Everyone I ask has a different opinion. The people in my bike store seem to have no clue or instrest. All the bike fitting companies only do a fitting for bike you already own so that's no help if I don't have one.

I am 5'10 and my leg in seam 32".

TIA

If there are five sizes in the range you are interested in, buy size 3 or 4. If there are four sizes, buy size 3. Obviously try them out in the shop if possible, but, as thelawnet says, you won't be too far wrong. Modern bikes are quite flexible in size as the frame allows for a lot of up or down movement of the saddle. Fitting and tweaking will come later when you might want to move the saddle up or down or shorten the stem.

[scottg]

I once had a somewhat too large frame, ended up with rather short stem.
On steep, 10% plus hills, the front wheel would come off the ground.
Not being Peter Sagan, I got good at standing on hills.
That bike was fitted over the phone.

Fortunately it was stolen, the replacement is a bit smaller,
front wheel stays on the ground now.
The builder of the replacement, asked for some numbers,
those were done the LBS, and sent off.

[whoof]

I am trying to buy my first road bike but have no idea about sizing. Everyone I ask has a different opinion. The people in my bike store seem to have no clue or instrest. All the bike fitting companies only do a fitting for bike you already own so that's no help if I don't have one.

I am 5'10 and my leg in seam 32".

TIA

Go to the bike shop and ask to test ride one with an effective 56 cm top-tube and with the saddle set so your leg would be pretty much straight whilst sitting on the saddle and your heel on the pedal. See how it feels and go from there, might not be spot on but it's a good starting point.
In the picture below the effective top tube is measurement B. That's the length of the tube if it were parallel with the ground not it's actual length.

[horizon]

In that example (and it's pretty typical), the OP only has two choices. He sits right on the cusp between two sizes (M and L) at 5' 10" but that probably won't matter as adjustments will cover the difference. Rule of thumb is to take the smaller. Job done.

I think people get a bit hung up on bike sizing and start thinking about all the other adjustments that will indeed need to be made in time but won't affect size of bike. Usually there is no choice at all - there is only one size logically to get.

[scottg]

In that example (and it's pretty typical), the OP only has two choices. He sits right on the cusp between two sizes (M and L) at 5' 10" but that probably won't matter as adjustments will cover the difference. Rule of thumb is to take the smaller. Job done.

Interesting, I'd tend to the larger, if I wanted less drop to the bars. Smaller frame for more drop.

[531colin]

Looking at that geo. table, the maximum increment in "reach" is 6mm for a frame size increment. That's less than the standard increment in stem length, which is 10mm.
So yeah, in that case, I would go for the bigger size to get relatively higher bars, on the grounds that you can reduce the reach to the bars by fitting a shorter stem.
The flipside of that is that you can have the bars as high as you like by fitting a steerer extender, provided its a metal steerer, not carbon.
That bike has fairly long head tubes anyway...…
.....and I think I'm beginning to see why the OP has a problem!
Incidentally, I think its a problem which could be solved by going to the bike shop with a mate who is a cyclist, rather than on the internet. The internet is a wonderful thing, but it can't go to a bike shop with you!

[whoof]

Looking at that geo. table, the maximum increment in "reach" is 6mm for a frame size increment. That's less than the standard increment in stem length, which is 10mm.
So yeah, in that case, I would go for the bigger size to get relatively higher bars, on the grounds that you can reduce the reach to the bars by fitting a shorter stem.
The flipside of that is that you can have the bars as high as you like by fitting a steerer extender, provided its a metal steerer, not carbon.
That bike has fairly long head tubes anyway...…
.....and I think I'm beginning to see why the OP has a problem!
Incidentally, I think its a problem which could be solved by going to the bike shop with a mate who is a cyclist, rather than on the internet. The internet is a wonderful thing, but it can't go to a bike shop with you!

That geometry chart was posted by me just to illustrate what effective top tube length was. I was suggesting a bike with about 56 cm effective top tube as a starting point. If I had to choose between bigger or smaller I would go slightly smaller rather than larger. But I don't ride sitting up right and I'm not offering advice to me.

[531colin]

We seem to agree that its difficult to offer advice remotely to somebody you have never met.

[Kamil1308]

I don't think it matters THAT much, unless you have had problems in the past.

I am 6'0" and have had 'M' and 'L' frames and am quite happy with either.

I would be looking at an M in your case although different manufacturers vary, but generally if you have a choice between two sizes probably go for the smaller one.

Thank you!

[Kamil1308]

I am trying to buy my first road bike but have no idea about sizing. Everyone I ask has a different opinion. The people in my bike store seem to have no clue or instrest. All the bike fitting companies only do a fitting for bike you already own so that's no help if I don't have one.

I am 5'10 and my leg in seam 32".

TIA

If there are five sizes in the range you are interested in, buy size 3 or 4. If there are four sizes, buy size 3. Obviously try them out in the shop if possible, but, as thelawnet says, you won't be too far wrong. Modern bikes are quite flexible in size as the frame allows for a lot of up or down movement of the saddle. Fitting and tweaking will come later when you might want to move the saddle up or down or shorten the stem.

Thanks a lot.

[Kamil1308]

I am trying to buy my first road bike but have no idea about sizing. Everyone I ask has a different opinion. The people in my bike store seem to have no clue or instrest. All the bike fitting companies only do a fitting for bike you already own so that's no help if I don't have one.

I am 5'10 and my leg in seam 32".

TIA

Go to the bike shop and ask to test ride one with an effective 56 cm top-tube and with the saddle set so your leg would be pretty much straight whilst sitting on the saddle and your heel on the pedal. See how it feels and go from there, might not be spot on but it's a good starting point.
In the picture below the effective top tube is measurement B. That's the length of the tube if it were parallel with the ground not it's actual length.

top.jpg

Will do. Thanks a lot.

[Kamil1308]

Looking at that geo. table, the maximum increment in "reach" is 6mm for a frame size increment. That's less than the standard increment in stem length, which is 10mm.
So yeah, in that case, I would go for the bigger size to get relatively higher bars, on the grounds that you can reduce the reach to the bars by fitting a shorter stem.
The flipside of that is that you can have the bars as high as you like by fitting a steerer extender, provided its a metal steerer, not carbon.
That bike has fairly long head tubes anyway...…
.....and I think I'm beginning to see why the OP has a problem!
Incidentally, I think its a problem which could be solved by going to the bike shop with a mate who is a cyclist, rather than on the internet. The internet is a wonderful thing, but it can't go to a bike shop with you!

Thank a lot for your help.

[Marcus Aurelius]

You’re not far off of my height and leg length.I reckon A 54 or 56 cm frame would be a good starting point, the 54 would probably give you a ‘twitchier’ ride, in comparison to the more relaxed 56. ‘Giant’ bikes would be a size M, as would something from Decathlon. Then you could get a bike fit done to tweak all the other bits and bobs, to get it bang on. Many decent bike shops will let you try different sizes out, before you commit. Look for one of those places.