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Discussion Starter · #1 ·
I have noticed that I seem to hit the pedals on objects or sometimes the large chainring will hit a log where it shouldn't. How much does 25% sag lower the BB height on this bike? Maybe the cranks are longer than normal or something too. Anyone else experience this? I saw about 6 yeti's on the trail the other day and one guy I talked to said the same thing. Kind of funny, he mentioned it while stating that his previous bike was an ML and he liked his 575 much better... :D Yeah, I know... Here comes the debate again..... :rolleyes:
 

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My guess...

iviguy said:
I have noticed that I seem to hit the pedals on objects or sometimes the large chainring will hit a log where it shouldn't. How much does 25% sag lower the BB height on this bike? Maybe the cranks are longer than normal or something too. Anyone else experience this? I saw about 6 yeti's on the trail the other day and one guy I talked to said the same thing. Kind of funny, he mentioned it while stating that his previous bike was an ML and he liked his 575 much better... :D Yeah, I know... Here comes the debate again..... :rolleyes:
If the specs show the BB height using a 140 mm fork at 13.75, and the travel is truly 5.75 in.,then subtract 1.44 in.(25%) from 13.75. You get 12.31 in. sagged BB height(aprox).
 

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Quattro said:
If the specs show the BB height using a 140 mm fork at 13.75, and the travel is truly 5.75 in.,then subtract 1.44 in.(25%) from 13.75. You get 12.31 in. sagged BB height(aprox).
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I see a small error there... we would need to get a 25% of the difference from the maximum BB height 13.75 and the minimum one (unknown), since the BB doesn't hit the ground at full compression (at least I hope it doesn't :eekster: )
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EDIT: I reread your post... and now see where you got the 25% percent... my only doubt is that I am not sure if the 5.75 travel is completely vertical... it could be just the axle displacement diagonally.... just a guess...
 

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In my mind, I can do it!
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Discussion Starter · #5 ·
Ok, according to this Linkage program here are the specs of what I see.

5.75" of travel = 146mm
13.75" BB heigth = 349
2" shock stroke = 51mm

So... @25% sag =
12.7mm shock compression = .5"
314.7mm BB Heigth = 12.37"
35mm vertical rear wheel travel = 1.37" or 4.38" left

I don't know how that compares to other bikes though.
 

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iviguy said:
Ok, according to this Linkage program here are the specs of what I see.

5.75" of travel = 146mm
13.75" BB heigth = 349
2" shock stroke = 51mm

So... @25% sag =
12.7mm shock compression = .5"
314.7mm BB Heigth = 12.37"
35mm vertical rear wheel travel = 1.37" or 4.38" left

I don't know how that compares to other bikes though.
iviguy, one question, are you compressing the fork to 25% too in Linkage or just the rear???
 

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Discussion Starter · #7 ·
crisillo said:
iviguy, are you compressing the fork to 25% too in linkage or just the rear???
I have the fork set for 20% sag and the weight distribution at 61% rear and 39% front.
 

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crisillo said:
EDIT: I reread your post... and now see where you got the 25% percent... my only doubt is that I am not sure if the 5.75 travel is completely vertical... it could be just the axle displacement diagonally.... just a guess...
I haven't put a caliper on a 575, but even if the travel is measured as an arc length, I can't imagine it's much different from vertical displacement; the static BB height is 1.25" above the rear axle (according to the yeti web site geometry chart), the main pivot is above that - I'd guess it puts the pivot such that the line between the main pivot and the axle is horizontal 1/2 through the travel. If that's the case, and 5.75" refers to the arc length, then the vertical displacement is 5.72".

This is one of those things I'm really enjoying about my hardtail. When I was riding a dualie, I never knew if my chainring was going to smack stuff or not - with the ARC I know exactly how much room I have before I hit. OTOH Yeti dualies actually have sag taken into account on BB height - a lot of dual suspensions just keep a 11.5" BB height (about what you'd want on a hardtail) then... whops, 25% sag lowers that an inch or more and you snag on every log you try to ride over.
 

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Joules said:
I haven't put a caliper on a 575, but even if the travel is measured as an arc length, I can't imagine it's much different from vertical displacement; the static BB height is 1.25" above the rear axle (according to the yeti web site geometry chart), the main pivot is above that - I'd guess it puts the pivot such that the line between the main pivot and the axle is horizontal 1/2 through the travel. If that's the case, and 5.75" refers to the arc length, then the vertical displacement is 5.72".

This is one of those things I'm really enjoying about my hardtail. When I was riding a dualie, I never knew if my chainring was going to smack stuff or not - with the ARC I know exactly how much room I have before I hit. OTOH Yeti dualies actually have sag taken into account on BB height - a lot of dual suspensions just keep a 11.5" BB height (about what you'd want on a hardtail) then... whops, 25% sag lowers that an inch or more and you snag on every log you try to ride over.
I see your point Joules.... Thanks for clearing that up... I didn't see it that way before...

Cheers
 

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I've got a trail on my property that I've been riding for over 10 years. The only frame I've ever built that causes me to hit my pedal on roots is the 575. I still have tons of Yeti love but, hey, it's a little different trail riding here in the southeast.
 

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Discussion Starter · #12 ·
mootsman said:
I've got a trail on my property that I've been riding for over 10 years. The only frame I've ever built that causes me to hit my pedal on roots is the 575. I still have tons of Yeti love but, hey, it's a little different trail riding here in the southeast.
Well, here is my theory on why this happens. You guys tell me what you think. My theory is that when you set your sag at 25% that's sitting still on the bike on a flat surface. I think that while riding your sag will be more pronounced which will lower the BB height further. The 575 is very supple and compliant.. ie... soft so you will be riding further into the travel while hitting the trail and the BB height will be lower.

If I were just guessing I would put the sag at 30-40% while riding the trail and probably hitting about 60-85% full travel while hitting roots and stuff. The cranks are 175mm I think so at 25% sag alone there should only be about 5.5" from crank bottom to the ground. At 50% into the travel there's only 4.9" from crank bottom to the ground and I would think you are at that range pretty often.

At 85% of travel, crank bottom to ground is only 3.6".

BTW - This is figuring for rear sag ONLY and is not even considering the fork sag into this figure.

I don't think I experienced hitting roots and stuff with the pedals when I was running at 20% sag but then again I wasn't getting the suspension benefit either. Guess it's just something we have to adjust for....
 

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Minimum clearance

Let the air out of the rear shock and measure the BB height.
 

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In my opinion, it is due to the fact that the 575 has a very linear linkage rate during thie middle of its travel, which causes the suspension to compress more over a given bump than a slightly progressive design would. If you have a slightly progressive linkage design, the suspension would tend to ride a bit higher midway through the travel.

Anyway, it's not really a bad thing, it is just something that you have to get used to. It is the same thing that causes the sweet bump absroption in the rough stuff.
 

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Actual measurements

I let air the out and measured the bottom of the BB (since that's what hits rocks, not the middle of the BB) and the bottom of the pedal to the floor.

175mm crank arms
2.1" Fire XC tires with no compression
Eggbeaters

No compression, BB about 12.5", pedals about 6.5" rounded off
1/2" compression on the rear shock, 11.5" and 5.5" rounded off
Full compression, bottomed out, 9.5" and 3.5" rounded off

I came off of a Gary Fisher Sugar, low BB and have been amazed at how good the clearance is on this bike. At first, I'd be bracing for impacts that just never happened. I guess it's all what you're used to
 

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Joeboater said:
I came off of a Gary Fisher Sugar, low BB and have been amazed at how good the clearance is on this bike. At first, I'd be bracing for impacts that just never happened. I guess it's all what you're used to
Very true - I came from a SC Heckler and found the BB to be lower on my 575. I'm getting used to it and it isn't a problem. I run a RP23 shock and notice it when I turn the Propedal off - the bike sits down quite a bit then.
 
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