Rival Spindle Degree

R

Ragnar

Member
Umax offers the 7/15 degree spindle option for the Rival. I know there are several threads on here that debate spindle degree. Most of which do not offer any simple conclusions.

Couple of basic questions:
1) On high bite tracks in adult clone classes is there any actual speed to be gained with this setup versus the 10/10 stock setup? If so, why?

2) Since the 7/15 option decreases camber gain and slows transfer is there a different baseline camber setup on the 7/15 versus the 10/10?

Thanks
 
Seems some disagreement on the effects of the spindle build angle.

Lf same caster and camber on either setup

Drawn in front plan view with tire in same spacer position on spindle axle, the tire contact patch moves farther from the kingpin axis with the 7.5 spindle.
Larger scrub radius with same caster should jack more weight on turn in.

Rf same caster and camber either setup

Same drawing with the negative camber, contact patch centerline moves closer to kingpin axis, so less weight jacking effect on turn in, if there was any to start with.

Because of the camber change curve, more weight is jacked on countersteer.

Caster affects how that curve is represented in relation to wheels straight ahead, vs turned.

Hope that helps.

I'd draw it out if I had cad capabilities.
 
#2 - I don't think it slows transfer. It may change when it transfers.
The 7* i think jacks less weight.
Funny that seems opposite what Mr . Shaw posted .
Wouldn't less angle move the contact patch closer to the king pin ? On the left.
 
Here is an image Al drew quite some time ago. The drawing incorrectly identifies the center of the contact patch, which also incorrectly depict scrub radius.
The angle for the spindle is degrees from perpendicular to the kingpin axis

Edit
All these images courtesy Al Nunley.
 

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With the static weights reset to same starting point, 7.5 build angle adds more weight to the lf/rr at same steering input for turn in.

Moving contact patch farther from kingpin axis does this. Same as adding a spacer, without widening front track.
 
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Running 10/10 compared to 7/15 has not effect on a straight line until you implement wheel input that’s where it all changes.

You can put the 10/10 set up on the scales. Set your camber/castor to a specific setting. Put that 7/15 set up on with the top heims jam nut in the same spot where the 10/10 set up was and your camber changes dramatically. Which it should happen because of the degree of the KPI.

Shaw is 100% correct on what he posted. Being able to stick camber gauges in both the lf and rf and actually turning the steering wheel to a certain point, you will see the change on how much camber the front wheels gain/loss and watch what the wheel weights do…….

There is speed in different kpi’s but not knowing exactly what it does can bite ya in the rear……

I sale all Umaxes with the stock 10/10. I know a lot of Burris racers go to the 7/15……. And there is a reason….. 🙂
 
JRC - Can you elaborate on the reason Burris racers go to 7/15?

We don't run Burris but I know guys that run 7/15 on Maxxis as well on bit up race tracks...and they are up front. Of course, they want tell you why.

Feel free to PM if you do not want to answer in this post.

Thanks
 
they offer it because theirs a sucker born every minute. With the exclusion of RF camber no factory driver I have ever talked to touches the front end. its factory caster, factory washers, factor L block, spindles, lead etc. They work their butt off mounting the seat just perfect add lead to get weight and win races. They adjust LF camber according to the available grip, the rest is tires tires tires. you will need to buy the matching L blocks as well so your looking at around $240 the set of tires that will buy is a better investment.. don't waste your money. get your kart set up well and figure out tires. thinking spindles will work magic is looking for an excuse for why what you got don't.
good luck and most important don't over think it.
 
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