Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

Can I use stack/reach to determine if a different frame size will fit?

Notices
Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Can I use stack/reach to determine if a different frame size will fit?

Old 12-28-20, 05:06 PM
  #1  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Can I use stack/reach to determine if a different frame size will fit?

My 2013 Domane Six Series 52 cm is damaged, and I need a replacement.
I can get a smoking deal on a 50 cm frame, 52's are very hard to find.
By researching stack/reach numbers from both a 50 cm & 52 cm frame, I believe that can do this.
Stack on the 50 is 15mm lower, that can be adjusted with spacers, I currently have a 5mm below the stem on the 52, it'll be two-10 mm spacers on the 50.
Reach on the 50 3mm shorter, I'll barely notice, or I can change stems.
The seat tube C-T is 25 mm shorter, but the long seat mast cap will be well within spec. I currently use the short version.

So, will this 50 cm frame fit?

Thoughts?
Dancing Skeleton is offline  
Old 12-28-20, 05:52 PM
  #2  
bruce19
Senior Member
 
bruce19's Avatar
 
Join Date: Jul 2006
Location: Lebanon (Liberty Hill), CT
Posts: 7,697

Bikes: CAAD 12, MASI Gran Criterium S, Colnago World Cup CX & Guru steel

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1397 Post(s)
Liked 778 Times in 467 Posts
You can fit a range of frame sizes. In my case, with a 32 1/2 " inseam it's about 54-56, although I can make up to a 58 work but it's not optimal. And, don't trust manufacturer's stated frame sizes. My CAAD 12 is 52 w/sloping TT. But, when actually measured with a virtual TT it's actually a 54. I'd start with inseam and go from there.
bruce19 is offline  
Old 12-28-20, 06:20 PM
  #3  
shelbyfv
Banned.
 
Join Date: Jun 2007
Location: TN
Posts: 8,083
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 2151 Post(s)
Liked 1,971 Times in 1,064 Posts
Sounds as if you will be fine. 20mm of spacers below the stem is not too much. If you can keep your stem between 90mm and 110mm that will be good as well. Probably more toe overlap than you are accustomed to but most folks can live with that.
shelbyfv is offline  
Likes For shelbyfv:
Old 12-28-20, 06:58 PM
  #4  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Originally Posted by shelbyfv View Post
Sounds as if you will be fine. 20mm of spacers below the stem is not too much. If you can keep your stem between 90mm and 110mm that will be good as well. Probably more toe overlap than you are accustomed to but most folks can live with that.
That's what I thought, I'm just not sure if I'll feel the difference in frame size, not sure if the bike will feel smaller.
Even if I do feel a difference, it may be because I'll be going from a 2013 Six-Series to a 2021 SLR.
Because of the endurance geometry & relatively long wheelbase, I don't think that I'll get toe-overlap.
I should add that I use a 100mm stem on the 2013.

Thanks for the input
Dancing Skeleton is offline  
Likes For Dancing Skeleton:
Old 12-28-20, 07:10 PM
  #5  
cxwrench
Senior Member
 
cxwrench's Avatar
 
Join Date: Jul 2013
Location: Nor-Cal
Posts: 1,298

Bikes: lots

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 528 Post(s)
Liked 617 Times in 352 Posts
The entire reason for stack and reach measurements is to do just this...compare different frames and determine if/how one will fit.
cxwrench is offline  
Old 12-28-20, 07:20 PM
  #6  
mstateglfr 
Sunshine
 
mstateglfr's Avatar
 
Join Date: Aug 2014
Location: Des Moines, IA
Posts: 12,268

Bikes: '18 class built steel roadbike, '19 Fairlight Secan, '88 Schwinn Premis , Black Mountain Cycles Monstercross V4, '89 Novara Trionfo

Mentioned: 97 Post(s)
Tagged: 0 Thread(s)
Quoted: 5008 Post(s)
Liked 2,316 Times in 1,361 Posts
Originally Posted by Dancing Skeleton View Post
Thoughts?
I think this is why stack and reach exist.
Sure it'll fit, but will it feel the same? Compare bottom bracket drop, fork trail, head tube angle, and seat tube angle.
Typically, the smaller the bike the seat tube becomes more upright and the head tube slacks out. But with you comparing one size different, hopefully all these numbers are the same/similar.
mstateglfr is offline  
Old 12-28-20, 07:24 PM
  #7  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Originally Posted by cxwrench View Post
The entire reason for stack and reach measurements is to do just this...compare different frames and determine if/how one will fit.
cxwrench,

Thanks for the reply.
Yes, I can easily make the effective geometry the same on both bikes, as I've done with the 2013 Domane & 2011 Madone H2 fit, both 52cm frames.
Will I notice the difference?
I don't get toe overlap on the 2013 Domane, I do on the H2 Madone.
I've read that you're a Trek mechanic.
Do you think that I'll feel a difference in the two bikes, and will that difference be more related to geometry or 1st generation vs current frame?
I should add that I'll get disc brakes on the new Domane.
Dancing Skeleton is offline  
Old 12-28-20, 07:32 PM
  #8  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Originally Posted by mstateglfr View Post
I think this is why stack and reach exist.
Sure it'll fit, but will it feel the same? Compare bottom bracket drop, fork trail, head tube angle, and seat tube angle.
Typically, the smaller the bike the seat tube becomes more upright and the head tube slacks out. But with you comparing one size different, hopefully all these numbers are the same/similar.
BB drop is the same, 8.0 cm
Trail: 6.0 on the 50, 5.9 on the 52
Head tube angle:71.1* on the 50, 71.3* on the 52
Seat tube angle: 74.6* on the 50, 74.2 on the 52

Wheelbase is 99.6 cm vs 100.3 cm

I'll do some research but I don't know how these affect the way that the bike will feel.

Thanks
Dancing Skeleton is offline  
Old 12-28-20, 10:30 PM
  #9  
cxwrench
Senior Member
 
cxwrench's Avatar
 
Join Date: Jul 2013
Location: Nor-Cal
Posts: 1,298

Bikes: lots

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 528 Post(s)
Liked 617 Times in 352 Posts
Originally Posted by Dancing Skeleton View Post
cxwrench,

Thanks for the reply.
Yes, I can easily make the effective geometry the same on both bikes, as I've done with the 2013 Domane & 2011 Madone H2 fit, both 52cm frames.
Will I notice the difference?
I don't get toe overlap on the 2013 Domane, I do on the H2 Madone.
I've read that were a Trek mechanic.
Do you think that I'll feel a difference in the two bikes, and will that difference be more related to geometry or 1st generation vs current frame?
I should add that I'll get disc brakes on the new Domane.
Between the 50 and 52? You most likely won't notice any difference.
cxwrench is offline  
Old 12-29-20, 12:24 AM
  #10  
SoSmellyAir
Senior Member
 
Join Date: Nov 2020
Location: Orange County, California
Posts: 160

Bikes: Cannondale Synapse, Trek FX 2

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 78 Post(s)
Liked 24 Times in 21 Posts
Originally Posted by mstateglfr View Post
I think this is why stack and reach exist.
Sure it'll fit, but will it feel the same? Compare bottom bracket drop, fork trail, head tube angle, and seat tube angle.
Typically, the smaller the bike the seat tube becomes more upright and the head tube slacks out. But with you comparing one size different, hopefully all these numbers are the same/similar.
Exactly. Even if we ignore feel, which also depends on frame material and construction in addition to the measurements, you need to consider at least seat tube angle in addition to just reach and stack to get an idea on fit.

Even a small difference in seat tube angle means the saddle may be so much further forward or backward that the change in distance cannot fully be compensated by the offset, depending on the existing offset of your seat post and saddle.
SoSmellyAir is online now  
Old 12-29-20, 09:35 AM
  #11  
DaveSSS 
Senior Member
 
Join Date: Sep 2008
Location: Loveland, CO
Posts: 6,272

Bikes: TWO Cinelli superstar disc with SRAM Force AXS

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 601 Post(s)
Liked 263 Times in 212 Posts
A common mistake made with this type of comparison is failing to correct the reach to the SAME stack height on both bikes. I bought two new frames with an 18mm shorter stack and 10mm shorter reach than my previous frames. The reach must be corrected for the 18mm of spacer needed. Use 3mm for each 10mm of stack height difference. That makes the new frame reach another 5-6mm shorter. In the end, I had a comfortable fit with 15mm of spacer and 110mm, minus 17 degree stems that I had kept around. 120mm stems would have been too long.

The difference in the STA does not impact the reach, but will slightly change the saddle setback needed to get the same saddle nose to handlebar dimension.

Last edited by DaveSSS; 12-29-20 at 09:41 AM.
DaveSSS is offline  
Old 12-29-20, 11:35 AM
  #12  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Originally Posted by DaveSSS View Post
A common mistake made with this type of comparison is failing to correct the reach to the SAME stack height on both bikes. I bought two new frames with an 18mm shorter stack and 10mm shorter reach than my previous frames. The reach must be corrected for the 18mm of spacer needed. Use 3mm for each 10mm of stack height difference. That makes the new frame reach another 5-6mm shorter. In the end, I had a comfortable fit with 15mm of spacer and 110mm, minus 17 degree stems that I had kept around. 120mm stems would have been too long.

The difference in the STA does not impact the reach, but will slightly change the saddle setback needed to get the same saddle nose to handlebar dimension.
Good points.
If I get this frame, I have enough stems on hand so that I can get the same effective reach. I won't change the saddle setback, since it's the same on all of my bikes and I don't get knee pain.
Dancing Skeleton is offline  
Old 12-29-20, 11:53 AM
  #13  
expatbrit
Senior Member
 
Join Date: Oct 2013
Location: 'burque, holmes
Posts: 820

Bikes: Ridley X-Fire (now an ex-bicycle), Trek X-Cal, Giant Defy 3

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 152 Post(s)
Likes: 0
Liked 16 Times in 13 Posts
Originally Posted by shelbyfv View Post
Sounds as if you will be fine. 20mm of spacers below the stem is not too much. If you can keep your stem between 90mm and 110mm that will be good as well. Probably more toe overlap than you are accustomed to but most folks can live with that.
Man. I'm bad. I run at least a 120mm and usually a 130mm stem
expatbrit is offline  
Likes For expatbrit:
Old 12-29-20, 12:04 PM
  #14  
Iride01
Hits [ENTER] b4 thinking
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 6,258

Bikes: '20 Tarmac Disc Comp '91 Schwinn Paramount '78 Raleigh Competition GS

Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 2427 Post(s)
Liked 1,121 Times in 823 Posts
Remember those stack and reach measurements are probably frame stack and reach to the top of the headtube/headset. So the other components on the bike that many times aren't included in the geometry specs can make enough difference to annoy you after the purchase.

While many times most mfr's use the same component sizes as other for a specified size bike, you still will be wise to pay attention as some don't. Take a close look at things like crank length, stem length, handlebar reach/drop and even try to find out how many mm of spacers under the stem that new bike will come with.
Iride01 is offline  
Old 12-29-20, 12:23 PM
  #15  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Originally Posted by Iride01 View Post
Remember those stack and reach measurements are probably frame stack and reach to the top of the headtube/headset. So the other components on the bike that many times aren't included in the geometry specs can make enough difference to annoy you after the purchase.

While many times most mfr's use the same component sizes as other for a specified size bike, you still will be wise to pay attention as some don't. Take a close look at things like crank length, stem length, handlebar reach/drop and even try to find out how many mm of spacers under the stem that new bike will come with.
I'm only getting the frame.
I've got all of the components from my current frame, which is damaged.
I've got plenty of stems & spacers to be able to make the contact points the same in relationship to each other as they are on my current bike.

Thanks
Dancing Skeleton is offline  
Old 12-29-20, 12:28 PM
  #16  
Eric F
Senior Member
 
Eric F's Avatar
 
Join Date: Jan 2020
Location: Altadena, CA
Posts: 686

Bikes: 2018 Storck Fascenario.3 Platinum, 2003 Time VX Special Pro, 1977 Nishiki ONP, 1999 Trek 9900 Team Issue

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 310 Post(s)
Liked 661 Times in 322 Posts
Originally Posted by expatbrit View Post
Man. I'm bad. I run at least a 120mm and usually a 130mm stem
Me, too. I ran a 110 for years, until it was suggested that I change to a 130 (by someone who knows about such things). I made the switch, and very quickly it was "Oh! THIS is how it's supposed to feel." 15 years later, I'm not as flexible as I used to be, but a low 120 still feels very right to my body.
Eric F is online now  
Old 12-29-20, 12:31 PM
  #17  
Eric F
Senior Member
 
Eric F's Avatar
 
Join Date: Jan 2020
Location: Altadena, CA
Posts: 686

Bikes: 2018 Storck Fascenario.3 Platinum, 2003 Time VX Special Pro, 1977 Nishiki ONP, 1999 Trek 9900 Team Issue

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 310 Post(s)
Liked 661 Times in 322 Posts
Originally Posted by Dancing Skeleton View Post
BB drop is the same, 8.0 cm
Trail: 6.0 on the 50, 5.9 on the 52
Head tube angle:71.1* on the 50, 71.3* on the 52
Seat tube angle: 74.6* on the 50, 74.2 on the 52

Wheelbase is 99.6 cm vs 100.3 cm

I'll do some research but I don't know how these affect the way that the bike will feel.

Thanks
It will probably feel different (depending on your sensitivity to such things), but not dramatically. A longer stem on a frame with shorter reach dimension will change your center of gravity over the bike a bit, but you're not doing anything extreme, so it should be all good.
Eric F is online now  
Old 12-29-20, 12:38 PM
  #18  
cruiserhead
Senior Member
 
Join Date: Dec 2007
Posts: 1,953
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Liked 6 Times in 6 Posts
stack and reach are same, head and seat angles are within half a degree. It will be fine.
the longer wheelbase will feel more stable, wanting to stay straight but may feel a bit less agile, depending on fork rake.

Originally Posted by Dancing Skeleton View Post
My 2013 Domane Six Series 52 cm is damaged, and I need a replacement.
I can get a smoking deal on a 50 cm frame, 52's are very hard to find.
By researching stack/reach numbers from both a 50 cm & 52 cm frame, I believe that can do this.
Stack on the 50 is 15mm lower, that can be adjusted with spacers, I currently have a 5mm below the stem on the 52, it'll be two-10 mm spacers on the 50.
Reach on the 50 3mm shorter, I'll barely notice, or I can change stems.
The seat tube C-T is 25 mm shorter, but the long seat mast cap will be well within spec. I currently use the short version.

So, will this 50 cm frame fit?

Thoughts?
cruiserhead is offline  
Old 12-29-20, 12:49 PM
  #19  
Dancing Skeleton
Senior Member
Thread Starter
 
Dancing Skeleton's Avatar
 
Join Date: Oct 2010
Posts: 354
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 20 Times in 15 Posts
Originally Posted by cruiserhead View Post
stack and reach are same, head and seat angles are within half a degree. It will be fine.
the longer wheelbase will feel more stable, wanting to stay straight but may feel a bit less agile, depending on fork rake.
Wheelbase is shorter on the 50 than my 52, so the 50 will be a little less stable & a little more nimble.
Probably very little.
Dancing Skeleton is offline  
Old 12-29-20, 08:03 PM
  #20  
cruiserhead
Senior Member
 
Join Date: Dec 2007
Posts: 1,953
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Liked 6 Times in 6 Posts
yup, sounds good
cruiserhead is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.