my 95 Q reacurring tire wear problem

[kbuck]

I hade 17 inch zenitti rims with 235/45/17 inch kuhmo tires, and this summer while driving on the highway the inner tread of the front left tire came off, I took it and got it aligned and they also replaced the tension rods and the a-arm in there, I got new tires put on because the old ones were worn so bad and didn't have any problems until recently I took off my rims to put the snow tires on and the tires were worn to the inside again, and now I'm lost because I had the alignment down and the camber taken care of before, so Im wondering what is the issue now, because I can't afford to keep buying new tires over and over again, and also with my aftermarket rims i was told i needed center hub spacers, well i never got them in from california but the dealer of the tires told me it wouldn't affect wear I'd just get some vibration, but now with my factory tires and rims, im still getting vibration, so Im figuring it's something I hope with the suspension. Help me out Please

[Q45tech]

Q45 have serious rigid suspensions: the amount of caster whichs adds camber in turns plus the static negative camber going straight ahead.

Anything over negative 1.2 degrees static front camber will wear tires [inside] FAST!Tires that don't wear are usually destroyed inside faster.

Nissan knew what would happen and fitted 170 [90-93] and 200 [94-96] tread wear index so the tires would get replaced at 15-18,000 miles........trying to get more mileage means buying harder compound tires and excepting all the downsides in wet and dry traction, that come with these hard tires.

17" less than ultra premium wheels can be a can of worms as you found out!.........as can Kumho tires.

[Gunman]

Q45Tech....

By "anything over negative 1.2 degrees static front camber" do you mean anything > -1.1 (-1.0, or any positive measurement) or anything < -1.3 (-1.4, -1.5, etc)?

I just did a realignment and had the front left come out at -0.9 and the right front come out at -1.5 (both within spec tolerances). The rear cambers came in at -1.9 and -1.7 (left and right, respectively).

Further, the tech said there is no adjustment for the camber -- so how do you adjust this measurement?

I also think I've read here that it's important to get the toe as close to zero as possible -- my measurement is within spec, but to the high side. I have a 3-year anytime alignment, so I can always go back and ask to have it redone...just want to make sure I'm suggesting the right changes.

NOTE: This Q had new Tokico blues at all four corners a year ago (10,000 miles), as well as new upper control arms and strut rods in the front.

[DAEDALUS]

Since we're talking inside tire wear, it is -1.3, -1.4, etc that will increase wear. All parts must be in good condition to meet the spec. The upper links are the most likely culprit if the camber is off, but if the other parts are worn, the upper links will wear out faster.

[Q45tech]

Any negative camber will shift the shape of the foot print......fattening the side with negative camber and taking away weight on the otherside.Radial tires need -0.5 to optimize design.

Every 0.1 degree is worse and worse but remember the center of factory [acceptable disregarding tire wear] range is -0.75 .degrees. [the rear is - 1.08 deg].

Use solid geometry and calculus to calulate the force differeces on different shaped tread patterns caused by camber!

Remember the alignment specs [the center numbers] are only valid for the oem tires with all new suspension. Different tires, worn suspension parts [rubber bushings in arms] will require different numbers ........thus the wide range.

With camber the force vector is not evenly distributed and the inside edge can see more weight per square inch [thus more faster wear].1 degree is 1.75%2 degree is 3.49%........this gets multiplied by a factor of 10 in trying to determine straight ahead wear.

Remember the caster adds to the camber in a turn so its not just the 1-2 degrees of straight ahead camber [and the 35% it might add] but the 6,7,8,9 degrees of new camber in a turn............at 8 degrees of rolling/turning camber the inside edge wears at 140-200% of the outside edge.

[Q45tech]

I just did a realignment and had the front left come out at -0.9 and the right front come out at -1.5.

The right side always gets worse faster. With new upper links and 0.7 excess camber you can always count on the lower a arm has a worn bushing and the third link is slightly bent and maybe the shock tower metal is bent slightly [or all 3] ...........somethings are not where they should be by almost [0.158795"] 0.2" [1.0 degree would be 0.22685"]

need 4 - 3/16" shims under the 4 bolts between the upper link mounting bracket and the shock tower metal.......the cheap temp fix.

[Gunman]

1) So would that be one 3/16" shim per bolt? Or four

2) What would be the more expensive, permanent fix? New lower arms, new links??

[Q45tech]

I changed everything : lower arms and upper links and third links around 120-140k to get back to brand new center of range specs.

At 240K I replaced the kingpins and bearing and wheel bearings and hubs........but I change upper links every 30-40k.

At 258k my front cambers are within 0.2 degrees of each other with my weight in the drivers seat!

My rears are within 0.1 degrees........when you run out of adhustment range you have to change things.

Keeping a 14 year old car as new dynamically is a challenge and not for those who have to watch their money.

[kbuck]

The local infiniti dealer here replaced a left front "knuckle" because when they showed it to me back in the garage, the mechanic grabbed the wheel and could wiggle it around freely, probably thats what is causing my front end to vibrate, The only thing I had a problem understanding is why would one knuckle on the left front throw the whole car out of alignment wearing tires like that?

[Q45tech]

The knuckles don't go bad the wheel bearings, tie rod ends, and kingpins [and its bearings] and things that attach to the knuckle go bad..

Pretty obvious that if you need to space the whole mounting assembly out 3/16 of an inch that you would place a SINGLE 3/16" shim between the chassis and EACH BOLT of upper link rear mounting bracket.........right.......otherwise the angle would change.

Don't assume that the average or lowest class technican at a dealership or even the Mastech [or Service Manager] at every one of the 165 dealerships is trained sufficiently in the older Q....especially the highest mileage ones.

Many of the best techs have abandoned the dealerships when times were tough back in the middle 90's........only recently has the search begun to find excellant techs, as sales have improved during the last 18 months.

The dealership standard are lose as a goose nd if it's in the FSM range it is ok...........WRONG.

[kbuck]

Hey thanks a lot for your help, you guys are the only ones that have any clue because the dealership just wants you out of there way so they just tell you anything to shut you up. I'll take a look into what you said, and figure out whats really wrong with the car.