Fork Pinch Bolt Torque

[Moparnut72]

I am replacing tires on my Mandello. When removing the front wheel the axle pinch bolts were extremely tight. In fact a couple made as best as I can describe lt creaking noise during the first turn or so. One of them was so tight I rounded the head over and had to drill it out. The 8mm wrench nor socket fit them very well with a bit of slop. A 5/16 SAE socket was actually tighter. I bought replacement bolts at the hardware store, they are much better. I was surprised that the hardware store had the exact same shoulder bolts. Anyway I looked up the torque value in the service manual which just short of 8 lb/ft for replacement. This seems to be a lot less than what it took to remove them. I haven't started to replace them yet as I need to pick up the wheel from the shop. I didn't want to change the tires myself in fear of scratching my beautiful gold wheels. Has anyone else run into this? This not the first time I have seen this type of thing. Comments?
kk

[ridingron]

Did you notice if the bolts had any kind/color thread locker on them?

[Oca Grassa]

I ran into the same thing on multiple fasteners on my Norge. Axle pinch bolts included. No locking compound on them…but dissimilar metals and a bit of moisture = galvanic corrosion.

I found this to be true on more than one bike bought from the used market. Between the gorilla tightened fasteners and galvanic corrosion I’ve ended up replacing a large number of fasteners on most of my bikes.

I’ve taken to smacking them with a hammer before attempting to loosen them. A mechanic I worked with called it giving them a “shock” before loosening to break the galvanic corrosion free. It does work but requires far more force from the hammer than some feel should be applied.

[John A]

It’s a place a where a torque wrench can get you in trouble. On the side that the large diameter of the axel goes through the leg you may notice that the fork leg is thinner around the axel. It will crack if torqued to the normal bolt value. A lot of them are bent there by over tightening if you look at bikes at a rally. Snug is all that is required on axel pinch bolts

[guzziart]

It’s a place a where a torque wrench can get you in trouble. On the side that the large diameter of the axel goes through the leg you may notice that the fork leg is thinner around the axel. It will crack if torqued to the normal bolt value. A lot of them are bent there by over tightening if you look at bikes at a rally. Snug is all that is required on axel pinch bolts

I agree that snug is good enough for these.  However Honda gives a torque value for fork pinch bolts in their shop manuals so a torque wrench would take the guess work out of the equation (I believe KTM did too) and that value is far less than it would be for a standard bolt that size.  It's gotta be a horrible feeling to over tighten and snap the bottom of the fork leg.

[n3303j]

...yet so many are proponents of the 108 ft/lb manual specification on T3 axle bolts when 25 ft/lb would do the job properly.

[guzzisteve]

Not caring, American hating factory worker thinking it's your warranty will fix it. Could also be a Turk they hired to save money.

[Moparnut72]

No thread locker. Also the bike is only a year and half old and is not ridden in the rain the V7 does that. I didn't use the torque recommendation for those bolts. Went by past experience as usual. I almost never use my torque wrench for the most part, head bolts for the most part. The factory bolts appeared to be zinc plated probably increased diameter a bit. I used the new ones from the local hardware store, much better but not great. The Mandello has two on each side, wasn't a pleasant experience dealing with the whole mess. Thanks for all the replies.
kk

Edit: The service station manual has a specific torque listing for these particular bolts. Turns out I didn't have the right adapter to be able to use my torque wrench anyway to see if it was a reasonable torque value anyway. The bolts, machine screws actually, didn't go in as smoothly as I would have expected, turning by finger until bottoming. Wasn't bad but not great. I would have chased the threads but the tap I had wasn't very good so I left them as is.

[John A]

For chasing threads it’s better to use a rethreader instead of a tap because a tap may remove too much thread . A rethreader just cleans and straightens the threads already there. It’s especially important in aluminum.

[guzziart]

...yet so many are proponents of the 108 ft/lb manual specification on T3 axle bolts when 25 ft/lb would do the job properly.

Yeah, good luck getting that axle nut loose, if you need to, on the side of the road if had 108 put to it previously.  Of course there are those of us (not me) that carry a battery powered impact or a cheater or two, sockets, air compressor,  etc.

Back to pinch bolts...iirc KTM spec'd 84 in. lbs. for the 8mm fork pinch bolts...not much.

[Oca Grassa]

84 in lbs=7 ft lbs = 9.5 Nm. Not much indeed. That’s 1/4” drive or T-handle territory where most are using 3/8 or 1/2” drive tools to “snug” those fasteners.

The tech data is available to use. Up to you whether you think you’re smarter than the engineers who spec that torque. Experience over my career working in and around aviation taught me to use the tech data.

[moto-uno]

  I have welded up more than a few lower fork legs from over torquing , IT'S CALLED A PINCH BOLT ! 

[Moparnut72]

I got everything back together. All went well for the most part. The bolts didn't go back in very smoothly i.e. not by fingers but I used the 1/4" ratchet and just snugged them up. I think maybe I should have used anti-seize but decided against it. I wonder if the plating (zinc?) contributed. When I worked in the aircraft shop I was tasked with installing studs in a Warner radial main case. They were going in so hard I was afraid of breaking a stud or galling the threads in the case. The boss wasn't concerned when I asked for advice, especially since the cases were virtually unobtainium. After still thinking about it through the years I believe the cadmium plating on the studs was responsible. It was a very stressful afternoon and I am  still cautious in similar situations.

Another question, the bolts or probably more correctly, machine screws, were hex headed. One of them rounded over because it as were the others that they turned very hard for the first few revolutions coming out. The hex heads on them are kind of tapered from top to bottom as were the replacements I purchased. Why is this? Ease of a socket on a pneumatic tool going onto the screw on an assembly line? Neither my sockets or box end wrenches fit very well. I am having a hard time describing this but hopefully well enough to make sense.
kk

[guzzisteve]

I'd put it up in air & turn axle till pinched & can't turn then go 1/8 turn more maybe 1/16, not much needed. Record the torque.

[Tom H]

You mentioned 4 pinch bolts, 2 per leg. I'm sure you know, when tightening them on the leg, snug up one bolt, then the other bolt and repeat until properly tightened and move on to the other leg. If not, you "could" crack the leg.

Tom

[Huzo]

You mentioned 4 pinch bolts, 2 per leg. I'm sure you know, when tightening them on the leg, snug up one bolt, then the other bolt and repeat until properly tightened and move on to the other leg. If not, you "could" crack the leg.

Tom

This…

[Moparnut72]

Like most things especially cases, work your way around in increments of torque. How many times do you see someone install wheels on a car going around the circle with full torque on the first pass.
kk

[MG_rider]

What  tomh says.

This especially applies to loosening the pinch bolts as well.  Likely contributed to the OPs problem undoing this joint.

When talking with the guru level mechanics in my area they tell me these pinch bolt joints are the most messed up bolted connections on bikes they service.

[Bisbee]

When I removed the caliper bolts to pull the front wheel off my 2017 Stelvio, the 3/8 drive was not enough. I used the long handle 1/2 “ and grunted . I retorqued them to 30 pounds per the spec after new tires. Maybe this is why AF1 sells titanium bolts for that purpose.

[Moparnut72]

None of the screws came out or went back in even when the weren't under tension. It seemed to me that the threads in the fork tubes were not as true as they should have been. Unfortunately in my small one horse town a thread chaser was not available. I could have ordered one as long as the tire change took. Since I have been out of action the repair shop was in no rush to change my tire.
kk

[Oca Grassa]

As I had no issues with either pinch bolts or caliper bolts on my Norge, I cannot comment on whether bolt quality or install prep was sufficient for purpose.

What I did note on my rear rotor was the screws were absolute garbage. The internal hex rounded out on all but one. When took a drill to the last one, which I had to drill the head off of to remove, I noted the hole was not centered on the head.

I thought I’d simply not centered the drill, but as I used the internal hex for that I wasn’t so sure. When I had a look at the other bolts, sure enough; even the unmolested internal hex was not centered. Asked my kid to verify that and he said it was obvious without close examination.

I replaced with Ti rotor bolts but wound up running a tap down each hole to clean up the threads. Lots of white powder came out which lead me to believe the bolts had been loctited in at install. Then I looked close at what came out of the last bolt hole, and it was clearly aluminum oxide.

Given the poor quality of manufacture of the bolts, and the presence of corrosion in the threads, I concluded the threads cut into the bolts was insufficient in outer diameter to fill the threads cut into the wheel hub. I gave the Ti bolts a liberal coating of copper Anti-Seize when installing. Should not be an issue in the future.