Bike Setup - Suspension / Chassis Flex

Slayer_1979
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Slayer_1979
Edited Date/Time 4/17/2012 3:47pm
I want to learn as much as I can about bike set up - suspension and or chassis flex. I just listen to a podcast with Rob Hendrickson the founder of RG3 suspension. The guy definitely sounds like he knows what he talking about. Flex in the suspension and bike chassis both attribute to the character and feel of the bike overall which changes how the bike handles, reacts and performs. These types of things intrigue me as I have an Engineering background. It seems like it's almost like a black magic and no one wants to share how it all actually works. (I know you'd have to be an Aerospace engineer to truly understand it). Someone has to be able to break it down into laymen terms right?

Examples:

Sand track I go stiffer on comp and slower on rebound since bumps are further apart, bigger and you hit them harder.

Hard pack is opposite I go softer on comp and faster on rebound since bumps are closer together and smaller usually.
(These are my opinions not saying they are right or wrong just what I go by for a base set up)

If you move the rear axle forward or backwards how does it affect the handling of the bike?
( I heard Mike Gosseler say that Ryan Dungey was very particular on exactly where his rear axle was set since it was change the feel of the bike that much)

How do different offset triple clamps affect the bike handling? Are they worth the cost?

How do different rear suspension links affect the bike?

I just thought some of you smart guys out there could help me out with these types of things? Any help, tips or insight you might have would be appreciated. Thanks and have a great day Smile
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mxtech1
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mxtech1 3/14/2012 1:21pm
3/14/2012 1:21pm
Slayer_1979 wrote:
I want to learn as much as I can about bike set up - suspension and or chassis flex. I just listen to a podcast with...
I want to learn as much as I can about bike set up - suspension and or chassis flex. I just listen to a podcast with Rob Hendrickson the founder of RG3 suspension. The guy definitely sounds like he knows what he talking about. Flex in the suspension and bike chassis both attribute to the character and feel of the bike overall which changes how the bike handles, reacts and performs. These types of things intrigue me as I have an Engineering background. It seems like it's almost like a black magic and no one wants to share how it all actually works. (I know you'd have to be an Aerospace engineer to truly understand it). Someone has to be able to break it down into laymen terms right?

Examples:

Sand track I go stiffer on comp and slower on rebound since bumps are further apart, bigger and you hit them harder.

Hard pack is opposite I go softer on comp and faster on rebound since bumps are closer together and smaller usually.
(These are my opinions not saying they are right or wrong just what I go by for a base set up)

If you move the rear axle forward or backwards how does it affect the handling of the bike?
( I heard Mike Gosseler say that Ryan Dungey was very particular on exactly where his rear axle was set since it was change the feel of the bike that much)

How do different offset triple clamps affect the bike handling? Are they worth the cost?

How do different rear suspension links affect the bike?

I just thought some of you smart guys out there could help me out with these types of things? Any help, tips or insight you might have would be appreciated. Thanks and have a great day Smile
The position of the rear axle effects how much weight % is distributed front to back. It effects the overall length of the bike, which determines how the bike turns. It also changes the length of the swingarm focal point and the amount of leverage it places on the shock.

Offset triple clamps change the rake angle of the front end. This can also change the weight % to the wheels.

Suspension links change the ratio at which the linkage arm pushes the shock. Simple physics here involving leverage arms and torque.

You have to realize one change/adjustment normally effects the suspension front and rear. changes/adjustments are not isolated the way one would think.

Suspension guys don't want to give up their information because it's probably the most difficult aspect of bikes to learn. It takes many many years of testing and building to really understand the mechanics and physics in the real world or racing. I'm the same way with my friends because i'm always willing to help them get their suspension dialed, but I always cringe when they start digging deeper for my secrets and setup tips.

I will give you one hint. Weight % on the front and back wheel are very important (I would say 2nd most important after sag.) I use digital bathroom scales and weigh every bike I setup. You will be surprised how far out of range your bike might be with a few ill-conceived adjustments.

If you want to learn alot, buy Paul Thede's suspension book from Race Tech.
Slayer_1979
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Slayer_1979 3/14/2012 1:47pm
3/14/2012 1:47pm
Mxtech1,

Now that's waht I'm looking for! Smile Thank you sir. Some easy to understand very useful information. I'll look into getting that book you mentioned too.

I usually try to change mine and my sons clickers per track depending on what type of track we are at. I no expert but I can tell you that just 2 clicks top & bottom can make a huge difference.

Most of my friends an a lot of other people I know NEVER change thier clickers. They will ride sand, hard pack, mud, loomy dry and dusty all with the same set up. I try and tell them to change it but thier always like oh no it's fine the way it is.

I race a little and the 30+ B/C level but mainly I'm a weekend warrior.

You sound pretty smart so seriouly THANKS for sharing what you can!
Falcon
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Falcon 3/14/2012 2:35pm
3/14/2012 2:35pm
Don't want to contradict MX Tech's very good info, but offset triple clamps do NOT affect the rake of the front forks... they change the trail, which is the length of the line from the contact point of the front tire to the spot in front that intersects the imaginary line drawn from the steering stem to the ground. Increasing the offset moves the forks farther away from the centerline of the steering stem when viewed from above and shortens the trail, whereas reducing the offset does the opposite.
Rake refers to the angle the forks draw forward from a vertical line, and is determined by the frame itself, via the steering tube. I think I remember hearing someone talk about making triple clamps that featured a different rake, but I cannot remember.
Falcon
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Falcon 3/14/2012 2:37pm
3/14/2012 2:37pm
By the way, one very effective adjustment is changing the ride height of your forks. Slide the forks up in the clamps to make the head angle steeper and the bike will turn faster, although with a tradeoff in stability. Slide them down for better straight-line stability but slower cornering.

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mxtech1
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mxtech1 3/15/2012 5:05am
3/15/2012 5:05am
Falcon wrote:
Don't want to contradict MX Tech's very good info, but offset triple clamps do NOT affect the rake of the front forks... they change the trail...
Don't want to contradict MX Tech's very good info, but offset triple clamps do NOT affect the rake of the front forks... they change the trail, which is the length of the line from the contact point of the front tire to the spot in front that intersects the imaginary line drawn from the steering stem to the ground. Increasing the offset moves the forks farther away from the centerline of the steering stem when viewed from above and shortens the trail, whereas reducing the offset does the opposite.
Rake refers to the angle the forks draw forward from a vertical line, and is determined by the frame itself, via the steering tube. I think I remember hearing someone talk about making triple clamps that featured a different rake, but I cannot remember.
Sir you are correct! Thank you for the correction. I knew I was meaning trail but my fingers must not have been thinking rake!

And yes, moving the fork height really changes handling. You can experiment with moving the fork height and rear axle position to get some very different handling feels.
Slayer_1979
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Slayer_1979 3/15/2012 8:52am
3/15/2012 8:52am
Mxtech1,

I have a question. Since % of weight to the wheel is very important can you give me a baseline to start from. This way I'll know if I'm in the ballpark or not. I'll do some testing and fine tune it according to my personnel needs after that.

Is it 60% rear and 40% front?

Maybe 50% rear and 50% front?

Is there a difference for a 4 stroke set up versus a 2 stoke setup? Maybe the % is a little different? Thanks man Smile
mxtech1
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mxtech1 3/15/2012 10:36am
3/15/2012 10:36am
weight % does seem to differ between 2 and 4 strokes from the best settings i've came up with. This seems to be because of the 4 strokes slightly higher center of gravity. the 4 strokes also seem to like a little bit more weight on the front wheel because of the tractable power - the rear of the bike tends to help steer so you can run a heavy front wheel % and have predictable steering. With the 2 strokes, we can usually keep the front end just a tad lighter because we need more weight on the rear because these bikes steer more with wheel spin and sliding (point and shoot)

Tell me what bike you ride, your weight, and i'll see what i have in my setup book that might help you get close.
Slayer_1979
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Slayer_1979 3/15/2012 12:56pm
3/15/2012 12:56pm
I have a 2009 CRF450 and I weight 145 lbs. If you have a setup for it that would be cool. I think I'm buying a 2012 KXF450 in in the next few months thought.
mxtech1
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mxtech1 3/16/2012 5:29am
3/16/2012 5:29am
Slayer_1979 wrote:
I have a 2009 CRF450 and I weight 145 lbs. If you have a setup for it that would be cool. I think I'm buying a...
I have a 2009 CRF450 and I weight 145 lbs. If you have a setup for it that would be cool. I think I'm buying a 2012 KXF450 in in the next few months thought.
55% rear 45 % front
Slayer_1979
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Slayer_1979 3/23/2012 9:24pm
3/23/2012 9:24pm
Thanks mxtech! I'll but some scales an check it out this weekend!
Riesenberg448 3/26/2012 11:31pm
3/26/2012 11:31pm
If you really want to understand suspension, I'd highly recommend Race Tech's seminars. Full disclosure, I am the Marketing Director for Race Tech, so I am definitely biased.

However, when I started my position I had zero idea about tuning suspension; I only knew what suspension felt like on the bike; but hadn't a clue about how it worked. I went to the seminar and learned a ton. I now can confidently change settings on my bike at the track to adjust to different tracks and conditions.

If you can't make it for the seminar, your next best bet is Paul Thede's Suspension Bible which is based on the seminars.

If you'd like more info on the seminars - here is a link: http://www.racetech.com/page/id/27

Here is a link to the Suspension Bible: http://racetech.com/page/title/Suspension%20Bible

I'd answer your questions, but as I said above; I am not a suspension genius, I leave that up to the techs at the shop. I can tell you, if you go through the seminar, you will immediately have full access to the RT staff to answer any questions you have.

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