JoeTBM 

We took in this used 26" Ladies NEXT Cruiser as a donation and noted that the fork just didn't look right and it ended up that the bike had a vibration, the lighter the person was that was riding it, the more the vibration was noticed and visible to an observer as well as the bike was just cruising at a slow speed (3-5mph). The vibration was best described as the same as when a wheel is out of balance on a car. Yes we did swap the front wheel assembly (rim, tube & tire) with a new one with no change so we believe we have taken the wheel out of the equation.

The fork had absolutely no visual signs of damage, buckling or chipped paint. It may have been a defect from the factory. The bike had very minimal signs of wear so it may have been donated because of the vibration issue.

We decided to try and do an alignment on it. We set it up with 2 pieces of 3/8" rod, one in each dropout to use as an alignment indicator with the ends facing each other, The fork's left blade was about 3/8" forward of the right fork blade. We purchase a used Park Tools Frame and Fork Straightener FFS-2 and attempted to perform the alignment, it worked pretty well and easily aligned the ends of the two rods. The issue is there is still a slight vibration felt in the handlebars when cruising at a fairly slow speed on level pavement.

We took a look at RJ's video on building a fork alignment gauge - but wonder if there is some a little more accurate/beefier that you may have seen or used.

Also, is there something else we are overlooking that could be causing the vibration? The bike otherwise is in very decent shape, better then most we get in, and hope to put is back on the road for someone.

Thanks
Joe TBM

Iride01 

Are you sure it's not that the down tube is pushed back changing the headtube angle and giving the wheel less trail?

3alarmer 

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...from the diameter of the frame and fork tubing, that looks like an aluminum alloy frame/fork,
You don't want to go bending and realigning aluminum alloy frames/forks for reasons that have been mentioned many times.

If it's steel, forget I said anything. There are other things that can cause vibration, mostly in the tyre and wheel. You can probably rule that out by spinning it fast in a wheel stand and seeing what happens.

Sometimes, Next bikes are better recycled through the scrap process than the renovation process.

canopus 

Park Tool FT-4 if you can find one. So simple... But went the way of the dodo bird with the rise of lawyers.

3alarmer 

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...oh yeah, one other thing that can cause a front end shimmy is the headset, either the adjustment or something else.
Usually that's not something that exhibits at low speed, but you might want to check that as well.

JoeTBM 

Fork and frame are steel

We did sub an entirely new wheel and tire/tube assembly as noted in the OP. Also vibration is only felt at a slow speed, coasting to a stop.

JoeTBM 

Downtube look straight, it was the blades of the fork that don't look right

JoeTBM 

That is our next try if the RJ alignment tool shows that we have corrected the bend.

JoeTBM 

Nothing out there on ebay or elsewhere we could find, thanks

canopus 

Yeah, It is going to take time to find one.

3alarmer 

...VAR made one, and Park made a couple of version (I think). They were never cheap to buy, and usually showed up in shops.
Shops all got rid of them years ago, because of liability issues. So for a while there were quite a few on ebay, but not so much any more.

I bought my VAR on ebay some years back, when I stopped spending so much time at the co-op, where we had a Park.

I recall seeing some plans for a homemade one, but I can't remember where. Sorry.

JoeTBM 

RJ the bike guy had on in a video that was homemade. We purchased the material to make one, we'll see how that works. I checked with our supporting LBSs but no one seems to have one to borrow and try (park tool version). We'll report back how we make out. The purchase of a new fork is not in the cards. The bike may need to be scraped if this last effort fails.

3alarmer 

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...if Stein Tool is still making and selling these, that's a good price, compared to what the used ones were selling for.

Frame and Fork Alignment Fixtures

JoeTBM 

3alarmer, we appreciate you finding this but the price is too rich for our volunteer shop. We just checked with the last LBS in our area to see if they had one for us to borrow but no luck.

Iride01 

Doesn't look straight to me, it's the lower curved tube. Not the head tube.

The angle of the head tube just doesn't look right too me. it's too vertical for a cruiser bike. Most cruisers, and actually most bikes in general have about as much angle to the head tube as does the seat tube, within a few degrees. You'd be surprised how many time I've seen posts where the OP had a head on collision with something and the fork was okay, but the downtube was bent putting the head tube at the wrong angle.

But it might just be the angle picture with the wheel turned a little to the side. For what the bike is worth, you have probably put too much effort in it already. IMO.

JoeTBM 

Yeah, it is not the best picture to show the issue and wasn't meant to be, just showing the type and style of the fork was the intent.

The headtube is straight, very easily witnessed when the fork is removed from the frame. We built the RJ frame alignment tool yesterday and it showed that both the blades of the fork were misaligned at the dropouts by 1/16"to the left so we reset that. While we had the fork straightener out again we also added a little more rake to the blades as suggested in a PM from another member here.

We are now waiting for our 90 lb. test subject to give the bike a ride and see if that helps, unfortunately she is not available until Wednesday.

As far as spending too much effort on this bike..... we have nothing but time and this has proved to be a good learning experience for our volunteer mechanics, the experience is invaluable.

Iride01 

Okay, like you I have no doubt that the head tube looks straight. What I'm saying it that that angle of the head tube appears to be wrong. Figure out what you seat tube angle is to the horizontal, and your head tube angle should likely be the same or within a few degrees. Though there are exceptions. Best would be to find the geometry specs for that bike or a profile pic of a brand new bike of the same model and compare.