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MEATengines

Oct. 19, 2022, 1:14 a.m.
Posts: 19
Joined: June 19, 2018

Posted by: fartymarty

A.funks - thanks for the reply.  Where do you measure your "effective stem length" from?  Is this from the centre of grips say 66mm from the end based on a 135mm standard grip length?

I use the measurement from dead centre of the grips. However in the past I’d considered this from different points - when pushing on the bars you load them from the rear of the grips, when pulling it’s from the front. You also need to consider the angle this is measured at - I feel it should be perpendicular to the steering axis as that’s constant whilst the force vectors into the bars are from many different directions.

Posted by: Ziggy

If you really want to nerd out on this stuff check out the ebook  “Dialed” by Lee McCormack. It’s a lot of info pertaining to bike fit- much of it counter to prevailing orthodoxy. He advocates grip center aligned with steering axis ( just to condense in case you don’t want to pay for it).

I discovered Lee’s book when I restarted MTBing in 2009 and followed his website etc closely for a long time. I experimented with his ideas of bike fit (RAD and RAAD) and on steering set-up and came to the conclusion that it didn’t work for me. And I mean really didn’t. I cannot stand that feeling of a zero ESL and (like many others) having moved to longer and longer bikes over the last decade I don’t think I’m suffering from Emperor’s new clothes when it comes to the pros of more reach.

I was quite reluctant to go bigger because I think he’s a good coach and has lots of great ideas on MTBing so I bought into his fit ideas for a while. I think I’ve gone from about 400mm reach to about 480mm (both at sag) on my hardtails between 2010 and now. Stack height has gone up a lot too, as that first bike had a 140mm 26” front end and my current hardtail is a 160mm 29”. I was concerned that the new bike would feel too big but it feels amazing and makes my full-sus feel a bit too short (but that’s a heavy ebike and has v long chainstays so is super stable and the wheelbases are v close anyway).

Oct. 19, 2022, 2:10 a.m.
Posts: 346
Joined: Feb. 24, 2017

Posted by: fartymarty

* I like ESL better as it describes what you are measuring.  I'm still not sure on LLB's horizontal measurement as the plane of reference is the steering angle / HA.

Yes. 

This is the problem with using stem length to adjust the fit of a frame, when you need it to dial in the handling instead.

Oct. 19, 2022, 5:52 a.m.
Posts: 375
Joined: Aug. 13, 2017

IMO stem length is all about handling.  Fit should be done with the frame size and seat position.

Oct. 19, 2022, 6:04 a.m.
Posts: 1671
Joined: Sept. 10, 2012

My personal bike fit process has always been:

  1. Pick frame size
  2. Set saddle vs. BB position for optimal pedaling
  3. Adjust stem length/bars to make fit work

My brain can adjust to changes in stem length/handling a lot better than my legs can adjust to changes in saddle position for best performance.

Not saying that's "RIGHT", but it works for me.

Oct. 19, 2022, 10:27 a.m.
Posts: 30
Joined: Feb. 24, 2017

Fartymarty, the sagged HA on the HT is 65.5, WB is 1118mm and FS is 64.8 with a WB of 1224mm.

The HT's fork is 120mm with a 44mm offset and the FS is 150mm with a 42mm offset. Front/rear center bias about the same.

For the record I'm a recovering XC/CX racer since the '80's with my first "trail" bike in 2014 so I think a +ELS comes naturally to me.


 Last edited by: joseph-crabtree on Oct. 19, 2022, 10:33 a.m., edited 1 time in total.
Oct. 19, 2022, 12:23 p.m.
Posts: 375
Joined: Aug. 13, 2017

Vik - it's the other way around for me as my Krampus and Murmur have very different seat / BB locations (despite having similar butt to bar measurements). 

Joseph - I've been a short stem guy for as long as I can remember.   My last "XC" bike was a GT LTS in the late 90's.

Maybe there is a NSMB article in all of this... (hint hint Mr Major - If nothing else it would be great to get something down for future reference and where various people are with various setups).

Oct. 19, 2022, 12:50 p.m.
Posts: 43
Joined: Feb. 8, 2022

TT.5

"bel-ray in the basement" had me howling! Admittedly felt like turning my water bottle away, hiding my Bel-Ray sticker... This past year for me has also seen "super lube in the side yard shed" and the shameful "castrol on the kitchen countertop". Some justification for having suspension serviced by the pros!

Oct. 19, 2022, 1:15 p.m.
Posts: 584
Joined: Jan. 2, 2018

I'm not convinced that handling and bike fit can be separated.

When I get my bars in exactly the right position relative to my pedals (in both the horizontal and vertical planes) , and by exactly I mean like a 5mm window, it totally unlocks the bike for me.

I have the right weight balance, the right amount of range of motion, and the right amount of biomechanical leverage to really take charge of the bike and not just be a passenger.

When I can do that, my bike handles great.

That's standing fit and that's what matters most. Then move the seat to suit.

Maybe if a frame happened to be just the right size (But they only come in 25mm increments so you'd have to get lucky) the ideal position for the scenario I'm describing would happen with the center of the grips lining up with the steerer but that'd be more confidence.

It would also depend a lot of the bars, as even with a 35mm stem you'll likely need to roll the bars rearward to "cancel out" them stem length. At that point you're reducing the effective upswept, which will alter your wrist and forearm geometry, which will also effect fit, handling, and leverage.

So given all that, good on you for having a reference point that instills confidence for you, but to me, chasing an arbitrary position of one component to another, at any cost, irregardless of the bike and rider as a *system*, is not something I'd be inclined to subscribe to.


 Last edited by: Kenny on Oct. 19, 2022, 1:16 p.m., edited 1 time in total.
Oct. 19, 2022, 5:53 p.m.
Posts: 30
Joined: Feb. 24, 2017

"When I get my bars in exactly the right position relative to my pedals (in both the horizontal and vertical planes) , and by exactly I mean like a 5mm window, it totally unlocks the bike for me."

I feel that humans are fairly adaptable as far as reach and that can be adjusted somewhat via handlebar rise and stem height but the steering feel, i.e. HTA/trail, weight distribution and ESL seems to be what I tend to focus on. There is 25+mm reach difference between my 2 bikes and it isn't an issue for me.

"even with a 35mm stem you'll likely need to roll the bars rearward to "cancel out" them stem length"

It all depends on how much sweep the bars have and where it begins from the center. A 12 degree Syntace bar has twice the rearward offset to the grips as a Truvativ Descendant so choose your bars accordingly.

Oct. 19, 2022, 9:22 p.m.
Posts: 81
Joined: Jan. 10, 2022

This stem length and bar sweep discussion is making head spin! I’d like to go to a shorter stem to see if my lower back likes it as much as it likes shorter chainstays, but then I’d lose bar height as well as saddle to bar length.  So then I’d add a headtube spacer to compensate for the height loss and shorten things more than expected. Alt-bars could bring things back even further, except that they don’t come wider than 780mm which means the width reduction brings me further forward than expected and changes my shoulder position…negatively? This changed position could counteract the 140mm—>rigid fork conversion in terms of descending comfort (if not speed) but I’m probably going to have to temper my expectations in terms of the berms and their self-railing antics. Also confusing is why the ESL and several other parameters are measured relative to the flat ground on which mountain bikes never actually travel. Do mullet bikes need their reaches defined to their slanted wheelbase lines, and for that matter will they roll backwards if released from rest on a perfectly flat surface? 

Am I allowed to temporarily ignore all this and say I just want a new stem because I think it will look nice?

Oct. 19, 2022, 9:46 p.m.
Posts: 346
Joined: Feb. 24, 2017

Posted by: Blofeld

Am I allowed to temporarily ignore all this and say I just want a new stem because I think it will look nice?

Absolutely! The stem is the key piece in the bicycle jewellery showcase.

Oct. 20, 2022, 12:03 a.m.
Posts: 375
Joined: Aug. 13, 2017

Posted by: velocipedestrian

Posted by: Blofeld

Am I allowed to temporarily ignore all this and say I just want a new stem because I think it will look nice?

Absolutely! The stem is the key piece in the bicycle jewellery showcase.

100% Yes.

Oct. 20, 2022, 1:17 a.m.
Posts: 375
Joined: Aug. 13, 2017

Kenny - I currently have a HT that has a 75mm shorter reach than my FS bike.  Both have a similar "butt to bar" measurement but are very different in geometry (old school HT and new school FS).  I like riding both as they are very different in terms of handling.  I can generally ride the same trails on both - maybe with the exception of super steep / tech trails which i'm not going near on the HT.  The HT is definitely too short at 440mm and the FS could be* considered too long at 515.  * depending on who you ask.  

As such the things I can control are the contact points and set up of bars / stem etc.  I think I am with Joseph on this one - that you can adapt - but it's still very much a "work in progress" and I don't think there are any right / wrong answers.  It's just nice to get some others opinions on it.

Blofeld - It is a bit of a minefield that isn't talked about.  I also agree stem length should be measured parallel to the stem, not horizontal.

Oct. 20, 2022, 7:01 a.m.
Posts: 1671
Joined: Sept. 10, 2012

Posted by: fartymarty

Vik - it's the other way around for me as my Krampus and Murmur have very different seat / BB locations (despite having similar butt to bar measurements). 

I find different bikes require a different saddle to BB relationship so I wouldn't try and match bikes in that regard, but I would setup the saddle to BB optimally first on a new bike and then adjust stem/bars to make it work.

Oct. 20, 2022, 7:32 a.m.
Posts: 30
Joined: Feb. 24, 2017

"Also confusing is why the ESL and several other parameters are measured relative to the flat ground"

ESL is measured perpendicular to the steerer axis centerline just like that new stem you are contemplating.

"I find different bikes require a different saddle to BB relationship"

Totally agree, my HT is more XC/ATB and saddle to bars it's 2cm longer and 3cm lower than the the FS bike as well as a 2 degrees slacker STA

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