Front end shudder at 130km

[hpras]

Hi All. 

My 87 FJ1200 has developed a pronounced, even alarming, shudder at 130km when pushing through a corner.  Feels like it's the front end wanting to wash out.  I tried to get my tire rebalanced, but it was good.  Redid the steering head bearings, top one did look pretty trashed, but no joy there, maybe a little better.  New fork oil while I was at it.  Played with the preload and damping, roughly the same feeling.  Can take the same corner at 120 or 140 and not feel the shudder, which led me originally to think it was the balance.  Have Bridgestone BT45's front and rear, about 3/4 through their life.  The front tire looks a little cupped.  Anybody have a similar experience?  Any guesses.

Hans

[andyb]

A new front tire will fix that every time.  As you keep riding it, it's going to happen at lower and lower speeds as that tire keeps getting worn funny.

At least that's been my experience.

[roverfj1200]

+1 tire... What you running

[hpras]

Was hoping that I could forgo a new set of tires for another season, they are stupid expensive in Canada.  I think this is the second time I've had trouble with Bridgestones, but the first time I put it down to having a set of Givi luggage and a tankbag on.  Tire selection seems rather limited here, Bridgestone or Dunlop GT501's.  Anybody have any luck with the Dunlops?  I've only ever tried the Bridgestones and the Michelin Macadams (no longer avaiable).

Thanks

Hans

[jvb_ca]

Was hoping that I could forgo a new set of tires for another season, they are stupid expensive in Canada.  I think this is the second time I've had trouble with Bridgestones, but the first time I put it down to having a set of Givi luggage and a tankbag on.  Tire selection seems rather limited here, Bridgestone or Dunlop GT501's.  Anybody have any luck with the Dunlops?  I've only ever tried the Bridgestones and the Michelin Macadams (no longer avaiable).

Thanks

Hans

Metzler LazerTech are still available for the FJ. Bias ply though. Buddy runs them on his 85 and loves em. Good mileage as well. A little pricey though.

Cheers...Jake

[andyb]

The FJ is going to cup pretty much anything you put on the front.  Lil more pressure helps, but can have some other issues with the handling and wear then.

Seems to be the cupping giving the weave.  If you go with a very triangular, racy front tire it happens easier and earlier in the tire's life... it'll also feel unstable in straight lines, but rail in corners.

[hpras]

Poked around a bit and see that quite a few people are running Avon radials on the 16" wheels on the '87.  Any general consensus as to whether running radials is a good idea or not.  I've vaguely heard pros and cons.  Most of my riding is town with the odd rip up the twisty road as needed.

[weymouth399]

I put one on this spring, got about 1500 miles so far. Juust starting to show wear for the crown of the road plus our local roads are very abrasive. Very round and it doesn't seem to have a very good contact patch either.
Bob

[hpras]

Ordered up a set of the Avon radials.  Will post my impression when I get them and have a good run.

Hans

[markmartin]

The FJ is going to cup pretty much anything you put on the front. 

I'm finding that out. Macadam cupped, Conti Road Attack cupped, and I've got about 3000mi + on an Avon AV55 and that is starting to cup.  The Avon has held up the best so far, however I've cut back on rushing every stop sign with a hard stop---I suspect this may be part of the cause.

[E Double]

I'm currently running Avon Azaro-ST tires on both the front and rear and I love them.  I have about 1,200 miles on them, and basically they're the reason I'm not in a hurry to buy a more modern sport tourer.  I had metzelers front and rear previously and the bike was slow to turn in, tramlined like a truffle pig and cupped like it was getting paid to do so.  I think one of the reasons front tires are quick to cup on these bikes is the amount of flex the skinny forks exhibit in transitions.  Hopefully my buddy will have the fork brace he's making for me done by the end of the week, and perhaps then tires won't be so quick to start cupping.  The Avons totally changed the personality of the bike.  The minute these tires stop being readily available is when I'll send this bike on its way.

[FJmonkey]

Ordered up a set of the Avon radials.  Will post my impression when I get them and have a good run.
Hans

I have a mostly stock 86' (16" Front & Back) and I run the Avon 45/46 front/rear and I like them. My tires before were a harder compound (good HD tire) with a less pronounced rounded profile. I had no chicken strips till I put the Avons on. The difference was night and day but any new tire that was not flattened out would have felt a huge improvement. I can't really comment on weather having radials is better for me or not. they are round, stick in the corners, great turn in and I can hold a line in a corner. Mileage on the front sucks for me as I live about 10 miles from some of best twisty mountain roads in SoCal (Angelest Crest Why). The heavy bike does not likely help with this either. The rear is starting to cup as I am about 3/4 through my second front. I am confident that I will get three fronts to one rear at the current wear rate. I like to ride into the corners so I don't brake into a turn. I set my speed and power out of the turn so hard breaking going in is not the cause. I actually try not brake at all as run up and down the Crest. Keep us posted on your experience and opinion of the Avons. Here is my first post on trashing the front Avon.
http://www.fjowners.com/index.php?topic=287.msg2088#msg2088

[vfourmax]

What are you guys running for tire pressures that are having the cupping problems? I have seen many instances of where people will set their air pressures on a cold tire that is at or above what the tire manufacturer recommends as preferred or ideal as far the hot tire pressures recommended. Differences of 3-5 lbs of pressure between a cold tire and a hot tire at operating temps is not unusual and can really make a difference not only in the way a tire wears but in the amount of contact patch hitting the asphalt. You would be surprised at how as little as 1/2-1lb of difference in tire pressure  can affect performance both in grip and wear and each tire brand and model prefers something a little different to be the optimum pressures for that brand and style of tires.

Incorrect hot tire pressures will definitely cause irregular wear, decreased grip and reduced mileage out of a tire. The average mechanic at the bike shop does not have a clue as to what the correct PSI should be. Your owners or service manual does not have a clue as to the tires on your bike either. If you really want to talk to someone that knows tires talk to the factory tire rep of the brand of tires you are running at a roadracing event or a well known respected tire vendor that deals with Vintage racing as they are familiar with the sizes and type tires for the older model bikes and what would be considered the ideal pressures for any given brand.

You would be surprised at how many will find out they are actually running 3-6 lbs more pressure in their tires than recommended by the manufacturer. Something else that many owners do is buy a 3.95 tire gauge from the local Auto Zone or PEP Boys and figure that their pressures are right because the gauge says so and cheap gauges are notorious for not being calibrated correctly, a good tire gauge will set you back at least 50.00-75.00 but will be something if taken care of will last you indefinitely just like any good tool.

Also you have to get into the mindset the tires are a consumeable commodity just like brake pads, oil filters and oil and so forth and high mileage vs. high grip are the opposite ends of the spectrum and the harder you ride the more this becomes a factor. Back in the days that I constantly road my FJ like a roadrace bike 2000 miles out of a rear tire and about 3200 out of a front was pushing it a bit. Now that I have slowed down my pace drastically I can get about 6000- 7000 really good miles out of a set before I think about replacing them. I do watch my tire pressures closely and when I take off a set to replace them they are worn down but still smooth and even. The only brand of tires I have ever had problems trying to get to wear evenly was Dunlops and no matter what I tried they would just not work for me.

Tire bills are a whole lot cheaper than crash damage because of worn, ratty tires.

[andyb]

Actually I'd have suggested the opposite, that a lower pressure leads to cupping faster, but wrong air pressure is definitely not going to help anyone.

Personally just go with the 10% rule myself, which works well enough.  Even so, the FJ has a tendancy to cup tires for whatever reason.  Fork flex sounds like a pretty realistic reasoning, never had a bike with so much weight and power and such spindly forks.

[markmartin]

What are you guys running for tire pressures that are having the cupping problems?

32psi-- cold this morning.  50 * F out door temp. sunny, and dry roads. Commute to work 22 miles, average speeds 120 50-75mph on a mix of straight and curvy roads.  Tire presure upon arrival 34lbs.

Two tire guages.  one cheapy, and one good one (but not $50 -$75)  same readings on both.

Most of the milage on my tires are typical to this ride.