Scorer75

Hi. First off, thanks to any and all that provide input and help.

I have a Cannondale CAAD 9 frame. The rear triangle is slightly "off". Using a digital caliper, it seems the rear wheel is offset towards the drive line side by about 2.5mm.

I know bending aluminum frames can be a bad idea, so as I see it I have two options, I'd like some input on these options, and any other ideas you guys may have.

Option 1: Have the wheels dished by 2.5 mm towards the non drive side. The problem with this option is I'll be limited to a single wheel set for this bike, and I'm not sure how the brakes will like working on a wheel offset that much. I prefer not to do this.

Option 2: Put a 2.5 mm washer between the rear dropout and wheel. This will resolve the offset, is not permanent, and would not require specifically dished wheels. My question is whether there is enough room on the wheel spindle to put a 2.5 mm washer, and still securely hold the wheel in place? Also, will this mess up the drive line, or can I adjust for that when I install the drive train?

Any body have any thoughts or experience with these two options? OR does anyone have another solution I should consider?

Thanks.

Wilfred Laurier

if the frame is indeed askew
then the wheel is likely not just translated to the side
but also slightly rotated out of plane with the rest of the frame
and there is nothing you can do about that

but i wonder if it really is askew
how did you measure it
did you use the string technique
or did you install the wheel correctly and then backwards
or did you install a known good wheel

or was there some event
like getting hit by a car
that makes a misaligned frame likely

Scorer75

Thanks for the response.

The wheel is not askew, just off center by about 2.5mm.

I measure this with a spare wheel that is true. I used a caliper and measure different points on the wheel against the frame, it is consistently off to one side.

The bike was not hit or damaged, let's just say this was a defective frame from the factory.

So assuming it is in fact only off center, anybody have any recommendations or experience they would like to share?

Bill Kapaun

Unless I personally check the dish of the wheel, I wouldn't assume it was correct.
Simply flip the wheel 180 degrees and see if your measurements repeat.
IF SO, the frame is off. IF NOT, the wheel isn't correctly dished and the frame is still suspect.

2.5mm is a bit suspicious in the fact if a 135/130 hub was modified to the "other" by simply changing the spacing, your offset would be 2.5mm

Wilfred Laurier

was the wheel you tested with
checked for correct dish with a dishing tool
or did you do the measurements with the wheel in correctly
and then with it installed backwards
because if not
then you did not do a definitive test

also
if you are the first owner of the bike
then cannondale should replace it under warranty

Wilfred Laurier

if the wheel is true but the correctness of the dish is not known
then you can ascertain the condition of the frame alignemt
by comparing the measurements from the correct wheel installation
to the measurements of the backwards wheel installation

if the measurements are similar but reversed when the wheel is flipped
then the frame is likely fine
but the wheel is off
if the measurements are completely exactly the same
then the wheel is good and the frame is off
and if the measurements are completely different
then both are screwy

also to the op
where did you take the measurements

and
i think the chainstays on cannondales are assymetrical

fietsbob

Ok, how did you determine the centerline ? to say which way in the frame is off?


check the dish on the wheel with a dish stick .. to see if it's off center..

after welding the Aluminum frames as a whole are normalized,
its like annealing, to take out stresses from aluma-welding ..

and then re heat treated as a whole for stiffness ..

it is what it is, Now. that's why I say check the wheel .

Scorer75

1. I took the measurements with the wheel inserted correctly and again with the wheel reversed. The results are the same, so it is not the wheel. I even tested with a different wheel, same results.

2. I used a digital caliper to measure.

3. I measure at the chain stays and also at the seat stays, same results, off by 2.5mm

4. I am not the original owner, so going back to Cannondale is not an option.

Anybody have any ideas??? Please?

bobotech

Flip the wheel so its inserted backwards like others have suggested and report back what you find. Most important step so far that needs to be done.

fietsbob

2.5mm is insignificant in the larger world of things to worry about..

Scorer75

ok, so what am I looking at in the real world building a bike with a rear wheel that is 2.5mm offset?

Will I even notice it?

Shall I correct it partially, say 1.5mm just to be on the safe side?

Any reason I cannot or should not put a washer between the rear axle and dropout?

Wilfred Laurier

if it were me
and it isnt
i would see if there is a spacer on the axle
on the side the wheel is further from
that could be moved to the other side

if you swap sides with a 1mm spacer
the wheel will be moved by 2mm

you could just put a spacer on the outside of the axle
the only drawback to this would be
difficulty in installing the wheel

to see if the misalignment makes any real world difference
see if you can ride it no hands
a bike that is significantly misaligned
is very hard to ride no hands

fietsbob

which side is 2.5 mm wider than the dead center line ?

alignment tables give accuracy... And I think you are within a margin of error without one..

with out actually having torn the bike down bolted the BB to the fixture on the big heavy table

and used dial micrometers to take the measurements this is a folly of obsessiveness
seen often here, because writing about such things is so easy.

the closing the rear QR will close the gap. its there to allow less effort removing the wheel.

sreten

Hi,

2.5mm offset at the seatstays and chainstays doesn't mean
the wheel is generally fully parallel and and offset 2.5mm.

It could be twisted along along a line between the two.

rgds, sreten.

FBinNY 

Frame measurement is more complex than most allow for.

For example checking the rim position with respect to the stays is just about meaningless. If you're measuring asymmetry at the seatstays, the centerline may be off, the wheel off plumb (leaning to one side), or the seat stays themselves are off, though the wheel is right.

Chainstay measurements are even more meaningless, since many chainstays are asymmetrical near the BB in order to improve chainring clearance.

So my advice, is to simply assume the frame is right, build it and see how it rides, and worry about alignment ONLY if it manifests classic signs of poor alignment.

Rule number one of bike repair ----Don't fix what ain't broke. Unless you identify the consequences of a problem, you don't have a problem to fix.

sreten

Hi,

I'd guess your best bet is just look at the wheel and the downtube.
If it just looks wrong it probably is, if it doesn't it probably isn't.

rgds, sreten.

Kimmo 

It's important to totally ensure your diagnosis is correct before proceeding. You could try clamping a straight-edge to the rim via a couple of spacers to clear the seat tube to see if it's pointing the right way.

If so, and your right dropout really is 2.5mm further from the centreline... or is that actually 5mm? I think it depends on whether there's a gap that has to be squeezed down... what's the distance between the dropouts with no wheel in there?

Be sure you fully understand what's happening here.

Option 1 is not so bad. The good news is, if you're correct about the frame, it's biased to the side you'd want it to be if it was intentionally asymmetric. And if you correct for it properly with dish, not only will the rim be perfectly centred in the frame and brake, but you'll have made your rear wheel stronger by adding NDS tension. And 2.5mm of chainline error on a multispeed bike is nothing to lose sleep over, unless maybe you're in the habit of small/small cross-chaining. Also, it doesn't mean you can't use other wheels, just that it won't be perfect, and IME this degree of misalignment is fairly common, lower in the market. You'd be hard pressed to notice it until you ride no hands, and then you might notice the bike has to lean over a tad to ride straight.

Option 2 will only resolve the offset if there's a 2.5mm gap to fill, otherwise you're spreading both stays and it gets a little tricky to figure out what's happening since they're not likely to spread evenly thanks to the chainring dimple. Less change to the chainline this way (not that it matters much at all) and you should be able to adjust it to work no problem. You only need a mm or two of axle in the dropout, but if you have conventional hubs you can move the axle over a bit if you like. Fails to take advantage of the situation to strengthen the rear wheel.

Jeff Wills

+10¹°°

I've heard of Cannondales that were out of alignment brand new that were straightened by a master mechanic who had access to a frame table.

OP: I would ride the bike. If it rides straight and fits you, stop worrying.

bradtx

Scorer75, Have a bike shop with a frame table determine where the frame is out of alignment. There maybe an easy fix.

Brad

PiLigand

It sounds like a few people may have touched upon this, but it isn't terribly clear from the language.

I've heard more often of dropouts not being entirely even and causing wheels to be slightly offset inside a frame. Though I've seen this mostly in no-name carbon frames direct from Taiwanese manufacturers, I guess there's still a vague chance that your cannondale is having the problem.

You may be able to determine this by using a level and some clever bracing skills. Install the wheel and see how it looks from bottom to top. If it is a bit crooked, then you can VERY SLOWLY AND CAREFULLY use a rounded file to take a bit out of one on the dropouts until the wheel sits straight.

Again, I've only seen this as a prominent issue in knock-offs, but just in case there's a chance.

bradtx

PiLigand, Seat stays (usually) and chain stays can be knocked slightly out of line by accident. The CAAD9, like a lot of other modern frames, has very few straight lines the home mechanic can reference to. A drop out alignment tool will certainly show where and just how much a drop out may need to be modified to realign the wheel.

Brad

FBinNY 

I repeat my earlier post. Build the bike and ride it before fixing what may not be broken, or making a fixable problem worse.

Short of having a frame table, or other plane from which to take consistent accurate measurements, it's impossible to identify the true nature of the misalignment (if any) and correct it. Alignment errors can add or cancel, so you need to see the big picture before starting in. If you measure one thing and "correct" it you might end up making things worse from a functional standpoint.

In the end, the only meaningful test of whether a frame is aligned decently is to ride it and see how it tracks.

Scorer75

Thanks so much for all the input, it's been tremendously helpful.

At this point, I'm going to complete the build and ride it.

If there are issues, I will go back to some of the simpler solutions posted, washer between the axle and dropout, then redish the wheel, and if those don't work, I'll go on from there.

bradtx

Scorer75, If the frame is at fault, and it reads that way, then redishing or shuffling spacers around will still leave a wheel misaligned in the frame and will only superficially be aligned at some aesthetic point. In other words it'll look fine, but still be incorrect. I still suggest having a shop look at it before the build and it probably won't cost very much.

Brad