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supermotard question

My two cents worth;
Not much difference going straight, though certainly not a gain of stability.
But in hard turns the loss a 'trail' is big. Trail is your feel, security and trust (or not) in the front wheel when leaning and turning. True sm bikes make up for this deficiency with special triple clamps to restore that loss of trail.

Stock your bike will have around 120mm of trail, 17" wheels puts that value to about 85mm. You can ride it, but not with abondon. You end up cornering slower, wondering where that good, secure feel went.

Any time you see a bike 'lose the front' it is for lack of trail. Like all those motogp stars you see on tv, tuck the front, yep, not enough trail for the available grip. period.
 

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Supermotard wheels on an '08... work great!

I just finished my Motard conversion on my '08 and I couldn't disagree more with Kent's diagnosis. I took a spirited 160-mile ride last Sunday morning and can say without a doubt that my bike is more stable at "sane" (under 90+)speeds than with the 21" hoop, also it now is much easier to initiate a turn or to make a mid-turn correction. There's a reason the SM guys use wide, sticky tires and it's called "traction". The bike is a whole different animal with these wheels on it. I tried to upload some pics but this darned forum won't let me even at the impossibly small size(s) specified. Check other KLR forums for more SM data and pics. Mike :35a:
 

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Create an account at photobucket.com then upload your pictures to there. Once uploaded, have the forum open and your album on photobucket opened. You then find the pic you want to post and click on the IMG option under the picture, this copies it, then here in your post you just right click and paste. Do a preview of your post and make sure the pic posted correctly. I also found out you can adjust the size of your pictures uploaded to photobucket, I use the 1024x768 option on photobucket, this makes a really nice big picture to see. Make sure to have the size option set before you upload. Hope this helps...
 

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motard question

It is okay for you or anyone to disagree with my comment, (not a diagnosis).
Besides our extensive geometry database of good and not so good handling motorcycles I base my comments on: All of our customer SM projects , using our good set-up with special triple clamps makes them several seconds a lap better than they went with the basic 17" 'motard set-up'. They tell me "it's like you gave me 20hp".
I have done the motard thing with a personal hotrod yz426, using 17" michelin roadrace rubber. Running very respectably lap times and racing in D Superbike, giving SV650's fits at little talladega. On one occassion I tucked the front at 80mph. crashed my brains out. 86.7mm trail on that particular set-up. I really needed special triple clamps, but I didn't want a dedicated roadracer out of my woods bike. I was just doing it for the fun of it.

Beware Emjayw and anyone else on 17" front wheels on dirt bikes:
Yes, the turn in is quicker, (because you have made the rake angle steeper with the smaller front wheel, and that is a benefit)you will tuck the front wheel at a slower speed and at less lean angle than with the 21" front (because of the loss of trail). fat rubber and all.

As I said previously, straight-line stability is not the problem. Deep lean angles, with tires near the edge of available grip is when it is deficient.
You wont get much warning when the front wheel tucks. It happens so quick.
Have fun and be careful.
 

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kent soignier ,

I was reading another post on this topic and wondered what you thought about it. This guy says he put a 17" wheel on the front so he could just carry one spare for both wheels, and also that with the 17" wheel and tires there is only a 1" difference in outside diameter.

I just wanted your opinion because it sounds like you know what you're talking about. I don't really understand the concept of rake and trail or why it matters. What's the difference between doing this on a KLR and an actual supermoto bike?

http://www.klrforum.com/showthread.php?t=5770&highlight=supermotard

Originally posted by: Rainier Tom

Here's the reason I laced up a 17" front wheel. If/when I take an extended trip on my KLR, instead of carrying two different sized spare tires, I could carry one spare tire (4.50"x17") and use it for either the front or rear.
The tire is a 120/90/17 Kenda K761 mounted backwards. A 21" front tire has an approximate diameter of 27 inches while the Kenda on a 17" rim has an approximate diameter of 26 inches (taller sidewall). You might want to build and install the front wheel first then decide how much to lower the rear.
 

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I wont comment on a conversion but wonder why the question of stability at speed was posed.Ive had a couple of klr's my newest an 08 and never have had a instability problem.
 

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supermotard questiion

sorry to be so long answering your question bethlehem. I have been at roadrace events for the last six weekends in a row, and full time at gmdatl. something like eight LONG days a week.

converting to 17 inch front rim so one spare tube fits both ends seems smart enough.
but I would not consider it a move for better handling until it is combined with the proper triple clamp offset to restore the LOSS of trail that comes with the 17 inch front rim.
Using a taller 120/90 series tire as someone mentioned will help reduce that loss but there is still a reduction of trail. I have not seen that combo so will reserve further comment.
if you don't intend to corner with roadrace style and commitment you will be fine.
the lack of trail doesn't matter
going straight, it really matters when you get down to extreme lean angles.
I have done this upgrade in chassis geometry for dozens of racers who started the process by simply lacing up the 17 inch front then telling me how wonderful it all is, then they lose the front end in a fast turn and crash.
after we put them on the Sweet Numbers their lap times improve to the tune of several seconds per lap. To a man they all did not realize how they had struggled to turn their bikes, since the tip in IS much better, but the TURN is not. I know that sounds oxymoronish, but trust ne on it.


remember, going str8 you'll be fine, turning at casual pace is okay too, the problems start when the pace escalates.
It is all in the numbers.
 

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I am in Kent's camp on this subject. His explanation is clear enough for a math challenged type like me to digest. I had no real understanding of 'rake & trail' until I started reading this thread.

Keep up the informative dialog Kent, I like the effect.

Ard
 

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Yes, thanks for the reply Kent. It's sinking in.

So I assume a basic rider like myself riding twisty backroads at the speed limit or slightly above would be OK? I don't lean corners like a pro or drag foot pegs and knees. I don't really understand how a triple clamp can help but it sounds expensive for someone like me who doesn't take too many risks anyway.
 

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Unless you are getting real spirited with the KLR, I don't see how converting to Motard would matter much at all. It will definitely feel different at any speed, but different doesn't automatically translate to better or worse.
 

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I wonder about lowering the rear end. A lot of people have to lower the KLR in the rear just because it's so tall. Wouldn't that affect rake and trail too?
 

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supermotard questions

yeah, the 17" front wheel looks very cool, simplifies the spare tube thing, and it works reasonably well if you don't ask too much from it.
At casual pace you would be fine.
At full tilt boogie every mm of trail matters.
If you lose the front wheel, called tucking the front, you'll know why.
Anytime you see the motogp riders (or anyone for that matter) lose the front end it is because there is not quite enough trail for the available grip. fall down, go boom. get up wondering wtf happened.
Trail is your communication with the ground. It is the feel you get as you push on the front wheel against whatever surface you are riding on.
Dirt bikes tend to have about 120 mm of trail as designed. My klr measures out to 127mm with the forks long in the clamps, and 117mm when I run it lower. I presently am running my front ride hgt 25mm lower, that is an inch of fork tube protruding above the top clamp. I can feel that deficit in trail but it is still enough for me to recover from a front wheel slide as my peg scrapes the asphault. so far
When a 120/70-17 front wheel/tire is installed that trail value drops to around80mm. That amount of trail will not give the rider enough warning as it approaches the egde of available grip. And it wont afford the same level of grip as 100 plus mm will. (Then there is: rear tire diameter, ride hgts front and rear, suspension damping and spring rates, triple clamps offset, etc. lots of variables and adjustables, with a small window where things are right, anything else is a compromise.)
The fact that proponents for the 17" wheels will holler about how much better their bikes turn comes from the fact that the smaller front wheel drops the axle enough to steepen the rake angle fairly dramatically (a degree or more) which is why the turn in gets lighter. This fools the rider into thinking the TURNING is better.
I have seen this many times and I agree, the tip in is easier, but it will not TURN as well. The steering suffers from lack of trail, the rider has to actually slow more to get the bike to turn, if the issue is pressed, you are rewarded with a tuck, boom. down you go. WTF, And it usually happens so fast you can not respond in time to save it.
 

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supermotard questions

yes bethlehem
changing rear ride hgt affects rake and trail. and swingarm downslope angle (which affects drive grip)
that is why I dislike the lowering links. Lower the rear end and you get a klr chopper (read; too much rake and trail). Unless the front is lowered an appropriate amount (not always an inch for an inch as many folks believe)
It is not that one cannot ride that, it just doesn't work as well as it could/should.

Sorry, I digress, I gotta get to work.
 

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yeah, the 17" front wheel looks very cool, simplifies the spare tube thing, and it works reasonably well if you don't ask too much from it.
At casual pace you would be fine.
Let me clarify things a bit. I'll soon be 55. Never had a broken bone and have no desire to have any. With a 17" front wheel my KLR still rides within my boundaries (read....skills). I have absolutely no desire to scrape pegs on either my KLR or my Strom.. With that said.....I like the look of a 17" rim on the front of the KLR.
Kent....good on you for keeping these folks educated. Serious...:)
 

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supermotard questions

I hear ya Rainer_Tom, pls, no broken bones. Keep it that way.

I too like the look of KLR's (and the like) with wide, 17", rims and rubber on them .

If clamps were available (but I don't know of any) to trick out klr sm's they don't really cost all that much in the grand scheme of things.
The clamps we use for roadracers, and dirttrackers, and proper sm set-ups tend to cost in the $650 to $900 range. There are a few companies that produce them, mostly to special order, for a select range of applications.

But no one makes them for the KLR as far as I know.
Probably not enough market to make prototyping and program justifiable.

Too bad because it transforms the way the bikes work.
 

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I just received my buchanan 3.5 X 17 front rim back. How much should I lower the rear?
 
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