Author Topic: KR200 Wheel Nut Torque  (Read 1449 times)

DrewS

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KR200 Wheel Nut Torque
« on: March 07, 2016, 09:41:09 AM »
I wonder if any fellow schmitters can provide me with some advice. I've been musing over the matter of wheel nut torque settings in relation to the KR200, are there any set parameters as is the case with modern vehicles? Thanks.
Late 63' Tiger Nose Schmitt pilot (In need of some TLC) 2004 Smart Roadster wearer (Yes it is a microcar at 698cc!! - Sadly Gone :-( ) Fiat 500 Owner (Tempremental, Poorly Built and with a wiring loom made of chewing gum and Spaghetti!!) and future Isetta or Trojan Owner ( As pocket money permits!!!

Big Al

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Re: KR200 Wheel Nut Torque
« Reply #1 on: March 07, 2016, 10:39:11 AM »
Never bothered really. Issue is what size studs and what wheels have you got. Early on the studs were 8mm? They were bolts with a tag to hold them in place. These habitually failed  leaving the nut and bolt to spin aimlessly. Then they tag welded the bolt head, these still fail.

It was realised that the studs needed tobe stronger all round so they went up to 10mm? These are much more reliable. Its not unusual for early Schmitts to be uprated to the bigger stud size.

The wheels came originally as a pair of rims. These proved inadequate and there were fatigue problems with the rims cracking. A centre circle was welded on to increase the strength of the rim. This worked. The later rims gained a bit more strength.

The rim bolts were reduced in number from the KR175 type wheel. Always check an unknown rim for fatigue on the rim bolt holes. They can fail. I have had one go on the road. Fortunately I felt it and had slowed before the wheel completely collapsed. Strangely these bolts are normally imperial - as the wheels were assembled in the UK, as each car kit arrived.

The factory seemed to use single spring lock washers to retain the nut. I tended to star washers as it spreads the load round the hole. Clearly the early version takes less torque before failing. I do mine to 'elbow' tight. That is a sharp pull upwards. But I am quite powerfully built on the shoulders. My guess is this will be about 40 lb ft. I have never had a nut undo. With the larger stud you can apply more. I do not as I found the way I did it worked.

If replacing the studs do not be tempted to use toughened type steel bolts. They are very strong, but they are not designed for shear force and can fail. The welding creates a fault in the steel, too. The idea is to use quality steel so it stretches a little. That keeps things tight. The material is actually stronger than the cap head etc to a shearing motion. For the same reason never use a loose cap head on an axle stand. A steel bar is safer. I currently have a BX engine half out as a previous owner replaced the proper mounting bolts with hardened steel ones. The three sheared level with the engine block. Engine out to resolve. If the mounting had rested on dowels there would not have been a problem, but it relied on just the bolts shaft.

Hope that helps.
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DrewS

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Re: KR200 Wheel Nut Torque
« Reply #2 on: March 07, 2016, 01:29:13 PM »
Thanks! I've purchased a complete set of new wheels from the club, complete with fastenings so hopefully this will be fine!
Late 63' Tiger Nose Schmitt pilot (In need of some TLC) 2004 Smart Roadster wearer (Yes it is a microcar at 698cc!! - Sadly Gone :-( ) Fiat 500 Owner (Tempremental, Poorly Built and with a wiring loom made of chewing gum and Spaghetti!!) and future Isetta or Trojan Owner ( As pocket money permits!!!