Handling question about turning

Serpexc · May 2, 2010

I went riding yesterday and my front wheel did not seem to get a good bite like usual. I had swapped over my KTM wheels that had new tires, but a one tooth larger rear sprocket. By moving my axle forward to adjust for the sprocket, did I screw up my settings so bad that I no longer have traction up front? The only other difference is that the new wheels were set up with Tubliss inserts, so they are substantially lighter than the wheels with UHD tubes that came off. What effect would the lighter wheels have on the suspension and what would I adjust to compensate? Thanks in advance.

steve · May 2, 2010

Moving the rear axle forward takes weight off the front wheel and can reduce front end bite.

Lighter wheels, or unsprung mass, makes for faster suspension response, so maybe adding a click or 2 of damping will help.

Is the tyre the same?

Steve

Serpexc · May 3, 2010

steve said:
Moving the rear axle forward takes weight off the front wheel and can reduce front end bite.

Lighter wheels, or unsprung mass, makes for faster suspension response, so maybe adding a click or 2 of damping will help.

Is the tyre the same?

Steve

I went from a well worn m59 to a new m403. I've had good luck with both tires previously. Add a click or two of rebound damping?

steve · May 3, 2010

Serpexc said:
Add a click or two of rebound damping?

and/or compression.

As the mass of the moving parts, ie wheels etc gets less, they move faster in response to a given impact. This means that it will compress faster, so more compression damping will slow it down. If you don't change the compression, the wheel will stroke/compress further, with the spring storing more energy, so it will rebound faster, needing more rebound damping to compensate.

Try 3 clicks more compression, test, revert, and try 3 clicks more rebound, revert and try 2 of each together. Test more options, but the above range should sort it, if its the reduced unsprung mass that is the issue.

My best guess would be to add 2 clicks of compression.

Steve

DaleEO · May 3, 2010

My two cents worth here...........

Other than moving the rear wheel slightly forward you have made some major changes that need to be explored further.

First of all you went from an M59 to a 403, and to top it off you went to a tubliss system from your 4mm tubes.

So #1 how much air pressure are you running in your front 403? #2 What rear tire are you running? #3 What type of terrain are you riding in?

Is it possible that you were running really low air pressure and the tire was rolling under? I just switched to the 403/404 combo and there was huge difference in feel from the old XCMH pirrelli's I was running. I'm still running 4mm tubes but with 15 psi in them for the desert. What I found was that compared to the pirrelli's the 403 front was VERY compliant, and it had really good traction in sand and on hard pack, way better than the pirrelli's.

What Steve said about the effect of less unsprung weight is true, your suspension, in theory would be more compliant, as with less mass the wheel will move more freely. The only place I part with Steve's advice is that I would put in some rebound first, as that usually helps front end bite. But his advice is sound, try it, keep notes and see what happens.

steve · May 3, 2010

Good point Dale, I forgot to mention that in my experience the Tubeliss is worth about 2 psi in tyre stiffness compared to 4 mm tubes supporting them, ie add 2 psi for the same tyre feel re sidewall stiffness.

If riding on rocks and roots, the rebound is the preferred fix, but softer terrain will respond better with a compression adjustment. The bottom line is to test.

Steve

CrazyTed · May 4, 2010

If you go over to KTMTalk you'll see a long discussion about the handling changes that the Neutech systems creates. All kinds of folks with many different opinions on how to fix it.

Also, about the Bridgestone tires. Any opinions and discussion on the M203 front and M204 rear tires? I have two in stock but absolutely no experience with these tires. I have worn out my MotoZ tires and they have been back ordered forever.

Serpexc · May 5, 2010

steve said:
Good point Dale, I forgot to mention that in my experience the Tubeliss is worth about 2 psi in tyre stiffness compared to 4 mm tubes supporting them, ie add 2 psi for the same tyre feel re sidewall stiffness.

If riding on rocks and roots, the rebound is the preferred fix, but softer terrain will respond better with a compression adjustment. The bottom line is to test.

Steve

2psi which way? I've found that the Tubliss set up makes the tire feel stiffer than the same pressure with a tube. I run between 12-15 with UHD tubes, but run 10-12 with the Tubliss. I was a fan of 12psi on the 505, but this bike seems to like 10 as of yesterday morning. I've run 8 in my 300. Great traction. 8)

Serpexc · May 5, 2010

DaleEO said:
My two cents worth here...........

Other than moving the rear wheel slightly forward you have made some major changes that need to be explored further.

First of all you went from an M59 to a 403, and to top it off you went to a tubliss system from your 4mm tubes.

So #1 how much air pressure are you running in your front 403? #2 What rear tire are you running? #3 What type of terrain are you riding in?

Is it possible that you were running really low air pressure and the tire was rolling under? I just switched to the 403/404 combo and there was huge difference in feel from the old XCMH pirrelli's I was running. I'm still running 4mm tubes but with 15 psi in them for the desert. What I found was that compared to the pirrelli's the 403 front was VERY compliant, and it had really good traction in sand and on hard pack, way better than the pirrelli's.

What Steve said about the effect of less unsprung weight is true, your suspension, in theory would be more compliant, as with less mass the wheel will move more freely. The only place I part with Steve's advice is that I would put in some rebound first, as that usually helps front end bite. But his advice is sound, try it, keep notes and see what happens.

I think it's better now. I ended up with 3 clicks of compression, 2 clicks on the rebound. While I was fiddling I ended up with another .half turn in on the high speed too.

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