[SOLVED] [Brompton] Small play between nut and locknut in headset
 

Hello,

I don't have another Brompton to use as a reference.

A couple of weeks ago, I had a Brompton-endorsed LBS replace the headset on the Brompton I bought years ago: The mechanic found the wheel didn't turn smoothly, and he suggested getting a new headset.

I just noticed that when applying the front brake and pushing forward, there's a bit of play between the nut and the lock nut. I don't have a 36mm skinny spanner, so could only use an adjustable spanner to check that the lock nut is tight.

Is that play normal, or should be there no play at all?

Thank you.

https://cimg1.ibsrv.net/gimg/bikefor...1cd1b55f52.png

Try tightening it a little and see if that helps.

Ok, I'll get a 36mm cone spanner. Thanks.

Yeah, if you own a bike with such a headset (and that's nearly all bikes for about 50 years and still being made) that spanner and a good, solid large crescent wrench are valuable tools.

When you do this, I suggest you first back off the locknut entirely. (sometimes but not always you can back it off and slide it up the stem. Other times the stem must come out or at least be lifted some. And loosening the stem can be an issue, but if that's the case, addressing the stem now instead of 10 years and weather from now will be a blessing you will won't regret. (Grease the bejeesus out of the stem's quill before you put it back in!) With the locknut off or lifted, look to see if there is a "key" on the washer; ie a small tab that fits into a machined slot cut vertically into the steerer tube. If so 1) hurray! Headsets without that tab can be one of life's lesser curses with the headset not wanting to stay tight and 2) you need to take reasonable care not to twist the lockwasher so hard you distort or shear off the tab. So grease the threads and the top of the washer. Turn the headset cup only when the lockwasher is loose, then hold the spanner and handlebar in one hand so it cannot turn and tighten the locknut with the other wrench against both spanner and handlebars.

That looks like a good, solid headset what should be a joy to adjust. And if it is of lesser quality, I am sure a stock and easily available Tange headset will be an very straight forward replacement.

The part in the lower right hand-side does have a tab, but I have no reason to try anything more than checking how tight the nut is since the whole thing is supposed to have been replaced a couple of weeks ago by a Brompton mechanic.
https://cimg9.ibsrv.net/gimg/bikefor...ac9def776b.png
https://curbsidecycle.com/products/b...-headset-steel

You will need two wrenches, just like doing cone nuts on axles.

Yes, a skinny spanner, and a regular adjustable/crecent wrench.

No Brompton user in the audience who could confirm that small play should not be there on a well adjusted bike?

Also, don't forget that tightening the nut is often a two man job as one person keeps the lower nut and assembly from turning leaving the other to concentrate on the top.

Don't forget to use "Lock Tight" on the parts. Mainly that is applying the lock tight to the threads and letting it dry completely before assembly.

Of course you know this...

Checked mine, I don't think it really noticeable. How are you inducing play?
Logically, there has to be a bit, but minimal.

I would differ with this. Having two nuts, one acts a jamb nut, so it should not loosen. I also would differ that it takes two people.

I pull the front brake tight, and push the bike forward. I can feel some play with my hands on the handlebar, or touching the nut + locknut while pushing the bike.

I know what a loose headset feels like (annoys me to no end), and I can confirm that it is not "felt" on my 2019 Brompton while holding the front brake and pushing.

Also, make sure to check that your front hub and wheel are secure, and that you are not feeling the play in the latching mechanism for the rear triangle.

Is it not possible for you to take it back to the shop that replaced the headset?

I find I am often tightening up a shade in the first 200 miles after setup. Also that not all mechanics now have spent a ton of time owning threaded headset bikes. Headsets can be set up a touch tight as when you mount the bike, you immediately squash the bearings a little with your weight, making them different from all the other bearing on the bike.

See my first post. I hold the handlebar and spanner in my left hand, crescent in my right. Bars both keep the wrench/cup from turning and make a great lever and handle.

Now it helps a lot that I keep my stems pushed down. (Gotta have the quill bolt reasonably tight also or the bars spin. Reasonably - no great muscle needed. A regular allen key should not be leaving an impression on your palm.)

Edit: never used Locktite on steerer thread. Rarely had any issues using headsets with keyed lockwashers and slotted stems.

Thanks much.

So I rode back all the way to the bike shop accross town. Turns out there was significant play between the nut and locknut.

Lesson learned: After replacing the bearings, even when done by a professional, make sure the two are tight — but not too tight.

Thanks everyone.

300 miles on mine has a bit of play, feels like a 1/16 at the handlebars, enough to notice.
Time to spring for a thin 36mm wrench