Dav305z

It's a Raleigh Grand Prix with 120 millimeter rear dropout spacing. I just got some Sun CR18 wheels with a 125 millimeter rear hub and a 7-speed Shimano freewheel. The wheel went in fine--just a little effort to spread the drops-- but the outer cog of the freewheel is too close to the drive-side dropout.

How do I fix this? Respace the axle? Cold set the frame to 125? Both? Or should I just go back to the 5 speed and call it a day? One other wrinkle in this tale is that earlier on I replaced the cottered crankset with a Velo orange compact double. It already threw off the chainline a bit. Will it be even worse with the wider rear hub/freewheel? Might this issue also be preempted by respacing/redishing the wheel? Finally, is this a job for a bike shop? I'm pretty good with tools but if it involves lots of finetuning I'm not sure I'll have the proper judgment. How much might I expect to pay a mechanic?

Doohickie

It's usually 126, not 125. Try putting a washer in on the drive side to push the frame apart just a little more. Once you figure out the right spacing, you can put the washer(s) under the locknut if you wanna get fancy. 126 mm should be okay for a 6 or 7 speed freewheel. If you want to cold set your frame so you don't have to stretch it every time, that's pretty simple, too. I have a big C-clamp that fits inside the dropouts and I just unscrew it to widen the spacing. Or you can get a piece of threaded stock, a couple washers and a couple nuts and use them to drive the dropouts apart.

dddd

There are many things that can affect the clearance for the chain not to rub on the frame.

The size of the smallest cog (bigger) may put the chain up against the end of the seat stay.

The way that the hub spacers/washers are set up on each end of the axle.

The type and even the brand of freewheel.

The type and width of the chain.

Generally you'll need only 3.3mm between the small cog and the frame for use with 8-speed width chain.

Spreading the frame won't affect the clearance by itself, since the frame will still sit exactly against the locknut surfaces when the QR or axle nuts are tightened.

I advise never spread a frame or fork by pulling or pushing the 2 sides against one another.
One side is always a bit stronger in terms of yield strength, and will bend first, putting the frame then out of alignment.
The frame needs to be bent out one side at a time, with progress measured carefully so that the wheel will still be centered after "spreading".
Also, one never knows how much of the spreading is elastic vs. permanent until the spreading device is removed, so many, many time-consuming tries might be required just to accomplish what will almost surely be an asymmetrical spreading.

The wheel in question could have the hub axle re-spaced, such that the 7-speed freewheel still gives the 3.3mm of clearance and with the over-locknut width set at only 124mm or so.
Just 3mm of protruding axle is needed on each end of a quick-release axle, so the original axlecan still be used. An assortment of different-thickness washers and spacers and a digital caliper are more than handy here.
The wheel would then need a little re-dishing, but this is the opportunity to get the spoke tensions optimized at the same time.

I just did exactly this with my PX10LE's rear wheel, and left the frame spaced at ~121mm. The wheel fits in easily, is very strong, and now I have 7 speeds.
I didn't have to spread the frame, but was able to keep the special fine-thread axle and cones from the Maillard "Prof'l Team Issue" rear hub.

Doohickie

I've spread frames and if it is asymmetrical, I can't tell.

Doohickie

Yep, that could work too.

Dav305z

So, do I also put a thinner spacer on the non-drive side or do I leave that entirely alone? Did you find the 7-speed offered similar chainline to the 5-speed when you were done? It's already borderline on my bike due to the VO crank (chain rubs the front derailleur a bit in the smallest cog) so I don't have much leeway.

due ruote 

Do you mean the chain rubs when you're on the small chainring? That's a combo you shouldn't be using anyway. If it's rubbing while on the big ring and you already have the FD maxed out, then you'll need to make a different adjustment, like using a spacer under the fixed cup.

dddd

At the rear, it would never be noticeable while riding, even though it might appear that the caliper were no longer centered over the tire, and/or the chainline noticeably altered.

At the front, forks are sometimes spread from 96mm to 100mm, and even a 1mm asymmetry can cause the steering to pull to one side.

Best of all, by bending each side separately, you can correct any existing asymmetry at the same time.

dddd

I would first measure the inside width between the dropouts, to see if it's actually 120 or a little bigger.

Does the freewheel or chain contact the frame, or does something first contact any axle-locating hardware that might be part of thederailer hanger bracket?
I did have to do some clearance grinding on the little axle stop bolt head that my frame used, to clear the chain itself. The earlier 5s freewheel also actually rubbed againt the axle stop bolt, but it was the freewheel itself and not the chain that rubbed
And, with the freewheel screwed on, how far does the axle locknut gripping surface extend outward from the outer face of the smallest cog.
These measurements would help determine what changes to make to the axle spacers for use with the 7-speed freewheel.
Note that a 6-speed freewheel is only a couple of mm narrower than a 7-speed freewheel, but that can be significant in cases like this

BTW, what kind of rim is on there, and is it 36-spoke? Is the axle nutted or quick-release?

On my wheel I believe that the chain now moves a couple of millimeters further in each direction after the mod's. The basic chainline is still well-centered between freewheel and chainrings.

Also, as was asked, is the front derailer maxed out as far as not being able to be adjusted to clear top gear (big chainring and smallest cog)?
That would then almost have to be a too-long bb spindle I would suppose, unless the cable needed tightening or the limit screw needed backing out.

GrayJay

Keep in mind that if you spread the stays, you should also re-align the dropouts so that they are again parallel. Particularly when using a freewheel type hub, non-parallel dropouts will make the axel much more prone to bend and then ultimately break.

A seldom mentioned strategy for cold setting a narrow frame wider is to only spread the drive side outward to achieve the desired wider spacing, leave the NDS stay as-is. This results in asymetrical spacing of the rear end but that can be an advantage if you then re-dish the wheel back to centerline of the frame to compensate for the dropout asymetry, side-to-side spoke tension of the rear wheel will be more equalized so produces a stronger wheel less prone to brake spokes and less of your weight is carried on the longer unsupported drive side of the hub axle so the axel is less likely to get bent. Produces a bit more clearance between RD and spokes too.
Downside is that it takes a bit more mechanical skill & care to asymentrically re-dish the rear wheel. Other compatability downside is that once the frame is setup asymetrical, swaping wheels from any other bikes adhering to the symetrical spacing standard results in mis-alignment of the rear wheel. Might be a problem if you were racing and needed to be able to get neutral wheel change but it is unlikely these days that a 7-speed steel bike is going to see such intense racing action.

Dav305z

The f derailleur isn't maxed out, but if I open it up any more, it rubs against the VO crank arms, which come in much tighter than the old cottered cranks did (BB is a Shimano cartridge with 127 mil spindle--I had the threads tapped for it). It all works--the rubbing I'm talking about is very minor--but I want to make sure as best I can that the 7-speed wont make it worse before I start modding the wheels and frame.I'll get exact measurements and pics later this weekend. Thanks for the input so far.

dddd

GrayJay made some very good points there, and it's a good idea to at least eyeball the dropout alignment on any frame, even if no spreading is needed.
I look for the derailer to remain stationary while the quick-release is tightened. Any rocking motion, however slight, indicates some degree of stress on the axle.

That is a bummer about the V-O cranks, as far as the close proximity of the arm to the big ring.
These cranks then, appear to be modeled after older cranksets which were designed around front derailers with totally flat outer cage plates and a fairly narrow cage profile.
The use of an inexpensive, fairly common Suntour MounTech front derailer should help immensely, so I recommend that be saurced as soon as is practical.
Hopefully no front indexing is used on this bike, but I have at least been able to use a Cyclone (double ring version) front derailer with Shimano's indexed front MTB shifters.
BTW, what kind and what sizes of chainrings are being used?

So really, the front derailer vs. crank arm issue isn't normally part of the chainline equation. This is a troubling limitation in terms of getting the rear wheel spacing/dish sorted out and I hope the OP can start with a front derailer that allows an optimized drivetrain! Perhaps V-O can offer suggestins about which front derailers are compatible with their crankset, and I don't think that it's too much to expect when you plunk down that kind of cash. At least you have the Forum people to fall back on in this case.

Bill Kapaun

I did something similar, changing an old 5 speed freewheel to 7 speed.
I then had trouble shifting back from 7 to 6.
The chain would hit the seat stay when trying to "rise back up" to the 6 cog.
I had to add about 3MM spacing to the DS.
I then had to redish the wheel, which resulted in very "vertical" DS spokes. Very little bracing angle.
I wouldn't trust that wheel to severe jolts, nor would I do it again.

dddd

Hopefully the OP's freewheel starts with a 13t cog, which gives a good bit more clearance than with a 14t cog for the chain to rise up during that shift from the smallest cog.

There are also 7sp freewheels with a 12t smallest cog, giving even more clearance for extreme cases where the seatstay end comes down low and to the inside.

irwin7638

It works. I did it on my son's Raliegh Gran Prix.

Marc

Charles Wahl

The idea is to have the rim centered on the frame's brake mounting hole in the brake bridge. Put the wheel in the correct way and tighten quick-releases. Mark on the frame, using a pencil and straightedge off the rim (w/o tire installed) where the edge of rim is. Loosen the wheel and flop it around to the other side -- installed with cluster on the "wrong" side. If the rim is in exactly the same place, then it's centered. You can also do this on a wheel truing jig, if you have one, or another frame -- it's all about the wheel being centered.

If the wheel is not centered within 1 mm or so, I'd do something about it. Add washers to one side or the other between the locknut and cone (I don't like adding loose washers to one side of the axle -- should be relatively permanent and not come between serrations on the locknut and the dropout itself). Or, have the wheel redished so as to be centered on the locknuts.

A lot of bike frames built for 126 mm spacing had the inside of right-hand chain (and sometimes seat) stay flattened to avoid the rubbing you're complaining about. Occupational hazard of cramming more gears in than the bike was originally intended to have.

You may move your crank right -- and it sounds like it might be a good idea to do so -- by installing a shim washer (preferably steel, but aluminum seems to be most available these days) between the fixed cup and the bottom bracket shell. Make sure that you have enough spare threads on the adjustable cup side, sticking out from the lock ring on the left side, before you commit to this. I wouldn't go over 2 mm. Chainline is chainline. Ideally, the center of the chainwheel(s) is about on the middle of the rear cluster, wherever that happens to be. Or, if you have a "happy gear" for most of your riding, you might bias the chainline to make that closer to no offset when engaged.

Captain Blight

Alternatively, you could just live with 6 speeds in back. Millions did for millions of miles.

Dav305z

This is starting to sound like excellent advice. I might even find an Ultra 6 Suntour.