OTK Rear Hubs

Chassis Setup, Tires & Handling Forum
1

I’m trying to determine what OTK rear hub I need to use so I can reach max track width of 55.125" with 6" rear wheels.

Using the standard OTK 1030mm axle and 50x92mm rear hub I can only get the track width out to ~53.25" (1352mm).

Do the 50x115mm hubs get me any wider? They have a second bolt which appears to take up the extra length. Can you run this hub with only 1 bolt tightened (nearest tire removed) ?

If not, then I guess I’m going to the 50x148mm hub. Just seems huge…

Thanks

2

Longer hubs does not. change the rear width.
But with std hub and 1030 rear alle you are supposed to get full width, its just a matter of sliding the hubs out far enough.

3

Question number one from me would be, why do you want to get to max rear width on 6" tires?

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4

The 53.25" I mentioned above, is with the 93mm hub slid all the way out with 180mm wheels (i.e. not 210mm). The width is 50.5" if all the way in.

This gets at the heart of my question, I guess. Do the longer hubs allow you to slide them any further out?

5

In my mind I’ve got 2 reason, but I’m open to being persuaded otherwise.

  1. We’ve got a couple races that have full sun and 106 deg. F air temperature. Last year my kid ran ~53 inches using hard tires but this season the spec is a softer tire. I can’t go any wider with the current equipment so wanted to plan ahead.

  2. I’ve picked up a kart myself. I’m 6’5" and 210lbs. Figure if my kid was at 5’8" 135lbs and we wanted wider, I’m really going to want wider in the same conditions.

What you think?

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6

I haven’t run 6" tires in a long time, so maybe someone else here has more recent experience. Is this for 206?

Totally understandable to want more rear track on a hot and sticky day. I just wonder how other 6" tire runners are dealing with that. Seems sort of grasping-at-straws to start running super long hubs to get the track width out there on that tire. One thing to remember is if you put a long hub on and just hang it off the end of the axle, there will be a lot of flex on that axle end, as there won’t be much axle within the hub, which will affect handling. On that note also, I wouldn’t run two-bolt hubs with just one bolt. That would be a lot of leverage on that one bolt, especially if the driver is 6’5" and 210 lbs.

Is the goal is to reduce weight-transfer? If so, there are lots of other adjustments I would try first before widening the rear out that far. I don’t know that I’ve really seen karts out at 55" on 6" tires. Reducing caster, lowering the seat or rear ride height, wheel changes, axle changes etc. all could solve your issue without resorting to the risk of losing a hub.

7

Thanks TJ and Bjorn, this has been helpfull.

I tend to focus on front & rear width because they are easy to adjust and I’m most experienced with them. Although, I think I need to change my perspective. I should:

  • Think of different length hubs as a method to stiffen the outer axle and less as a method to modify the width.
  • An older post by TJ also pointed out the 50mm axle doesn’t respond that much to stiffening by the hub and to prioritize front end geometry or axle stiffness to achieve desired results.

P.S. Yes my question is in relation to LO206 classes

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8

That sounds like a rear wheel with a very deep offset maybe?? What kind of wheel - spun aluminum Douglas?

Are you mandated to run a 6” wheel or just a 6” tire? You can run a 6” tire on a 210mm wheel and get some additional width easily enough.

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9

A lot of handling comes down to the ratio between width and CG height. If you can’t chase more width easily, you can still increase that ratio by dropping height. I actually prefer playing with height since it doesn’t dramatically change stiffness of the kart like width changes do.

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