790 Adventure R - Front Brake Issue

It was new..odometer 1 mile.

I asked because of the tires. I don’t remember hearing anything about Kenda big blocks becoming the OE tire.

It's an AdvS, they dolled it up into a faux AdvR, put big blocks on it, high front fender, and an Akrapovic.

Gotcha.

Taking mine in today for the recall.

There is a front recall now?

Seems like European dealers are all on the same page regarding the front recall, but North America dealers are a pretty spotty regarding knowledge/acceptance of the recall even if you tell them about it.

do we have an ID number that we can share with our dealers? And what are they changing out? The Mc?

https://advrider.com/f/threads/ktm-...-recall-safety-warning.1498563/#post-42244531

Apparently they are changing the return spring on the front master cylinder. I don't think that will fix the problem. It may cause or contribute to rotors warping. Friction equals heat build up. But the more obvious problem for me it the grabbing sensation when applying the front brake. Changing a spring won't change that.

The recall is to bring the 2019 & 2020 model front master cylinder up to 2021 specs. It won't cure the "warping" issue but it won't make it worse either, that's a totally different issue. The spring is a return spring for the master cylinder piston that will allow the brake system to "recharge" from the reservoir when releasing the brake lever. There have been instances with some bikes, including mine, when the brake lever would not return properly after squeezing the lever, creating a fair bit of slop in the lever. It was also more difficult than normal to bleed the system since one would have to wait for the master cylinder to fill up after each squeeze.

Hi all, not sure if this has been posted previously, but I just resorted to stripping my discs off and checking hub runout. the wheel was rotated on the bearings, so real life check. see sample pic below.

anyway, 0.08mm of one side and 0.07mm on the other. and i wouldn't expect to see any runout all all... No wonder the discs are giving issues.

back to dealer tomorrow.

(for record, I am only posting this to support the people on this forum who suggested that this was the issue, because I never heard of this happening before and wouldn't have thought to check)

Thanks. Next question. Is the runout caused by warp or uneven mounting to hub? Dealer found very similar runout on mine and called it a warp. Warp (according to KTM ) is wear and not covered by warranty.
If it's uneven mounting is will be covered by warranty, because it is not wear.
Or so I'm told.
They sent me new rotors, not under warranty. I had the original rotors checked by a different dealer. They said the rotors had uneven wear, but no discernable warp. Problem return ~ 3,000 miles later. Back to dealership, again diagnosed as warped rotors and not covered.
Please keep us posted.

What is the published spec for hub runout?

.08mm = .00315"
.07mm = .00276"

Can you clarify for me, total run out is approximately .0004" (pretty insignificant) or is the total sweep of the dial is -.008mm to +.007mm on your dial = 0.15mm (6 thou ish a major problem for sure)?

9 1/2

I just went through a copy of the Service Manual and couldn't find any reference to hub runout. Maybe KTM and/or dealers know? Gotta think it should be close to zero because if the plane of the hub mounting points are not true, the disc(s) won't be either.

I think those two measurements were for left and right hub surface runout, not readings for one side. One (or both) hubs could be bad due to machining or coating issues.

That's great you took it upon yourself to measure this. My bike doesn't exhibit the issue but I had suggested people do just that, to help diagnose the problem. That isn't much runout though, and wouldn't expect that amount to cause the problem(?).

quick answer to all;
the values quoted were sweep of the dial, on the left and right sides.

and 0.08mm = 0.00314" or 3 thou, which I do consider quite a lot. Personally I think that anything over 1 thou would be unacceptable. Any runout on the carrier mounting surface will be accentuated at the brake surface.

normally hubs are machined so that the bearing surface and brake surface are machined in the same operation to give zero runout.

(to give context to my comments but not to claim too much knowledge, I am an trained engineer running an engineering business, and have fixed/ridden/raced bikes nearly all my life)

Hi, I am reporting measured HUB runout. If you bolted new rotors to my bike I would expect a problem to develop again. Like yours appears to have done. my rotor runout was up to 0.2mm

If I don't get a new wheel I will remachine the disc mounting pads so they have no runout.

I cant quite tell from your post, but it seems you have only checked the disc runout? If you have never checked the hubs then you should certainly do so. as i mentioned earlier, I appreciated the comments on this thread that suggested this, because never before have I seen this type of problem and may have wasted a lot of time before finding it.

I found a discussion of hub runout on a Norton site, of all places, .25 runout on the hub was causing this same problem:
https://www.accessnorton.com/Norton...-to-cause-a-pulsing-brake-at-low-speed.23214/