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Understanding reach and ETT

April 4, 2019, 11:28 p.m.
Posts: 374
Joined: May 11, 2018

Can someone explain how reach affects handling?

If you have two bikes with the same ETT but one has a longer reach due to a steeper STA, how does that effect the handling? I understand that the steep STA improves climbing by altering your weight over the back tire but I am curious how the reach number effects handing. 

Thanka

April 5, 2019, 8:03 a.m.
Posts: 488
Joined: Jan. 31, 2005

If two bikes have the same ETT but one has a steeper seat tube angle then it by definition has less reach. Is that what you mean?

ETT and Reach


 Last edited by: craw on April 5, 2019, 8:04 a.m., edited 1 time in total.
April 5, 2019, 10:52 a.m.
Posts: 4857
Joined: Nov. 25, 2002

^the steeper sta bike would have a longer reach. longer front-center = more stability as wheelbase grows.

April 5, 2019, 3:55 p.m.
Posts: 657
Joined: Feb. 24, 2017

according to the image above, the ETT would change with the STA and ESTA but not the reach. the reach is relative only to the bottom bracket.

April 5, 2019, 5:49 p.m.
Posts: 488
Joined: Jan. 31, 2005

Posted by: xy9ine

^the steeper sta bike would have a longer reach. longer front-center = more stability as wheelbase grows.

Whoops, yes you are right. If ETT remains the same as the STA steepens then reach gets longer and the portion of ETT behind the BB gets smaller.

You have more weight forward so it's easier to keep the front wheel weighted while climbing.
The steeper the STA the weirder it feels pedaling on flat ground. 
A reach number on a relatively slack STA bike is not comparable to a reach number on a steep STA bike. The steeper STA brings you forward and consumes a ton of that reach, making that seemingly huge number not so big in practice. Read AMajor's review of the Kona Satori for more on this.
Taller riders are way forward than on old bikes which had the same STA and chainstay length across all sizes. Way further forward which makes it easier to keep the front wheel planted when climbing, which is amazing. Less hovering on the nose of the saddle.


 Last edited by: craw on April 5, 2019, 5:55 p.m., edited 1 time in total.
April 5, 2019, 10:47 p.m.
Posts: 374
Joined: May 11, 2018

I guess I should have been more clear in my question. I understand how a steep STA helps with climbing, what I am wondering is how two bikes with the same ETT but different sta and thereby different reaches handle while descending or cornering out of the saddle. 

The bike with longer reach/steeper STA will put the feet slightly further back in your stance, can someone explain how this effects the handling? I always figured it probably wouldn't make a lot of difference once you were out of the saddle but some guy in a bike shop was trying to sell my wife a size down even though the top tube is on the short Side for her because he thinks the reach is so huge.

April 5, 2019, 11:40 p.m.
Posts: 657
Joined: Feb. 24, 2017

can someone explain how this effects the handling?

not with any degree of meaningful accuracy.

April 6, 2019, 7:01 a.m.
Posts: 39
Joined: Nov. 14, 2017

Over the last few years I have gone from riding the recommended medium to large frames.  Once on the same model frame.  I feel more stable and comfortable descending.  Cornering is just as good or a hair better.  With my feet further away from my hands I can lean over the front end without feeling that OTB is imminent.  It is probably to do with my shorter legs, longer torso and, arms.  I have not seen a downside.  If I listened to the majority of riders and shop people I would still be on a medium.  I suggest trying both sizes with the correct stem and careful setup.

April 6, 2019, 7:54 a.m.
Posts: 3502
Joined: Dec. 17, 2003

Posted by: legbacon

Over the last few years I have gone from riding the recommended medium to large frames.  Once on the same model frame.  I feel more stable and comfortable descending.  Cornering is just as good or a hair better.  With my feet further away from my hands I can lean over the front end without feeling that OTB is imminent.  It is probably to do with my shorter legs, longer torso and, arms.  I have not seen a downside.  If I listened to the majority of riders and shop people I would still be on a medium.  I suggest trying both sizes with the correct stem and careful setup.

Longer front centre is good for straight line descending and higher speed. Most important when standing. You can be more centered on the bike (with reduced feeling/risk of OTB) which allows you to have more front wheel braking grip. (More confidence in the steeps and under braking).

You also HAVE to be more forward when cornering because you have changed the front rear balance of the bike if the FC measurement has grown out of balance with the rear centre. 

Longer FC takes weight off the front wheel, longer RC puts weight on the front wheel. But that's ok because you're more confident all round because of the other handling traits.

April 6, 2019, 11:27 a.m.
Posts: 193
Joined: Jan. 2, 2018

Simple. Add 35mm to the reach and subtract 35mm from the stem length and consider how that changed where your grips are relative to the front axle.

With the shorter stem and the axle moved forward, when  you weight the front of the bike, that force is closer to inline with the front axle, rather than out ahead of it. And you can shift your weight fore and aft and it still stays "in between" the two wheels. You have a bigger sweet spot in terms of body positioning and are able to weight the front end with less risk of OTB events.


 Last edited by: Kenny on April 6, 2019, 11:33 a.m., edited 1 time in total.
April 6, 2019, 11:51 a.m.
Posts: 1092
Joined: Nov. 8, 2003

I did some unscientific biased field research on this a couple years back with different sized bikes on Whistler laps.

My experience was that there's a definite limit to how much reach feels good descending (contrary to what you sometimes hear). Too long and finding the balance point front to back in turns became vague. You want your Captain's chair to be in one spot.

Mind you the longer the reach got up to that tipping point the more stable and awesomer everything got. Go too far though and it's like commanding the Starship Enterprise by yourself.

Ascending is a different story IME, long and forward is infinitely wonderful.

Now that the seat tube angles have jumped forward about a mile I'll need a new round of research when I buy a new bike. I have no idea how my established ideal reach numbers will play with new school ett numbers. That seems like a tricky balance.

Side note to avoid confusion: Reach is distance to bars out of saddle, ett is distance seated.


 Last edited by: Hepcat on April 6, 2019, 11:53 a.m., edited 1 time in total.
Reason: "Hi Crime Stoppers'., Hi Steve!
April 6, 2019, 3:56 p.m.
Posts: 42
Joined: Dec. 1, 2008

Posted by: RAHrider

Can someone explain how reach affects handling?

If you have two bikes with the same ETT but one has a longer reach due to a steeper STA, how does that effect the handling? I understand that the steep STA improves climbing by altering your weight over the back tire but I am curious how the reach number effects handing. 

Thanka

Keep in mind that noone can test the effects of reach in isolation. Ceteris paribus longer reach means longer wheelbase which also affects handling (e.g. more straight line stability). Or if you keep wheelbase fixed for different values of reach, chainstay length has to change which also affects handling, but in a different way.

April 8, 2019, 12:30 p.m.
Posts: 1532
Joined: July 11, 2014

I am dumb and can't get my head around how steeper STA requires longer reach for descending (standing). I get the steep STA = more reach required for seated climbing, makes total sense. My current bike is 460 reach, 74ish STA (offset bushings and overforked) with a 35mm stem. Say I bought a new bike with the same HTA but a steeper STA around 76-77 degrees and it had 480 reach. Isn't it going to just feel 20mm longer when I am standing? If I am happy descending with my 460 and 35mm stem, why would steeper STA require more reach for me other than the climbing argument?

April 8, 2019, 1:16 p.m.
Posts: 1177
Joined: Sept. 30, 2006

Posted by: grambo

I am dumb and can't get my head around how steeper STA requires longer reach for descending (standing). I get the steep STA = more reach required for seated climbing, makes total sense. My current bike is 460 reach, 74ish STA (offset bushings and overforked) with a 35mm stem. Say I bought a new bike with the same HTA but a steeper STA around 76-77 degrees and it had 480 reach. Isn't it going to just feel 20mm longer when I am standing? If I am happy descending with my 460 and 35mm stem, why would steeper STA require more reach for me other than the climbing argument?

Im with you on this one.  Reach is measured from the centre of the BB upward and intersects with a horizontal line from the centre of the headtube.  The STA has zero effect on this number, it is static number based on those criteria.  As stated before, ETT length can be thought of as the 'seated reach' while actual reach would be the 'standing reach'.

April 8, 2019, 1:19 p.m.
Posts: 3502
Joined: Dec. 17, 2003

Posted by: grambo

I am dumb and can't get my head around how steeper STA requires longer reach for descending (standing). I get the steep STA = more reach required for seated climbing, makes total sense. My current bike is 460 reach, 74ish STA (offset bushings and overforked) with a 35mm stem. Say I bought a new bike with the same HTA but a steeper STA around 76-77 degrees and it had 480 reach. Isn't it going to just feel 20mm longer when I am standing? If I am happy descending with my 460 and 35mm stem, why would steeper STA require more reach for me other than the climbing argument?

It wouldn't; as you said. It would mostly affect your seated climbing position. Reach is from the BB forwards. 

All the DH/park bikes that are never pedaled, could have 90deg SA and the reach wherever was comfortable.

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