Gillparis

Hi all.

I haven't posted in this part of the forum before. My own bikes are 1970's town/road bikes but I picked up a mountain bike for free for my husband. It is just missing a rear wheel and freewheel, which I know how to replace. It appears to date from around 2000.

However I am a bit confused about wheel size. The front rim is a Mach1 559x21c. Before I spotted this I was just looking at 26" wheels without paying much attention. But now I see that the one I was going to buy is 19c. The tyre is a Maxxis Adventure 26x2.1. So back to the drawing board.

Do you have any recommendations for rims and tyres that I could put on the back that would be similar? My husband is really not going off road, except in the forest with our 6 year old, so something basic really. It has rim brakes and a 7 speed shifter for the rear.

Thank you for any tips.
Gill

dabac

You can safely ignore the ”c” and buy the wheel you were considering.
559 is the Bead Seat Diameter - where rim and tire overlap - in millimeters.
The 21 - and the 19 - is the rim width in millimeters.
While most prefer to use matched sets, a 2mm difference in width isn’t going to hurt anything for casual riding.
If mismatched, I’ve heard people prefer the widest to go at either end.
Some prefer rear, to get a bigger air chamber, a bit more pneumatic suspension out of the rear tire.
Some prefer the front, as keeping the front wheel gripping is more important than the rear.
As for tires 2.1” is a very common width. If you ride mostly easy, smooth trails, feel free to go a bit narrower. If you like to ride bumpy, lumpy or soft surfaces, make a guesstimate to how much wider you can go.
I like the Conti Race Kings, but that might strike you as excessive for the planned use.
Schwalbe Smart Sam is good value for money.
Be wary of 26”. There is something like 5 different and incompatible wheel sizes using 26” as part of their name. The millimeter size is easier to get right.

Gillparis

dabac Thank you! I had associated the 2.1 with 21 and thought I needed a 21mm rim to go with a 2.1 tyre.

70sSanO

Just to reinforce what dabac stated, 559 iso/mm is what you need to check when shopping for 26” rims and tires.

Since it is an iso size, it should be marked with it somewhere on the item.

John

Gillparis

Thank you. It was 559 so I think I am OK. I have literally had it in my basket for a month and haven't had the courage to buy it. Parts for my old bikes cost a fundamental amount less and I can sell them on for the same price if I mess up 😊. But then they aren't new. I tried to find a used rear wheel for this but no luck.

dabac

You’re welcome!

Tyre/tire width vs rim width is one of the most tolerant fits on the whole bicycle.
The BSD - with VERY few exceptions - has to be spot on, but there is plenty of leeway WRT which width tire goes on which width rim.

Gillparis

dabac If you have the time could you help me out with a question.

I ordered the wheel and everything came and went together nicely. Then I have a problem mounting it on the bike. The wheel as a quick release on the axle. In hindsight I should have ordered a normal one but I just did the same as the front. Of course I forgot about the rear derailleur, which has a claw that sits on the outside of the dropout and therefore increases the width. The axle doesn't reach the outside of the drive side dropout.

Is there a solution, like a longer axle? Could I remove a spacer from the non drive side and move the axle across? Or change the size of the spacer on the drive side. But then the rear dropouts would need to be either squeezed in every time or reset, which I am not capable of doing. They appear to be 142 between the dropouts. If I have to change the axle is it better to put a traditional type with nuts on?

Never simple.

​​​​​​Many thanks
Gill

Any other advice gratefully received.

Gillparis

Having checked a bit more I need a longer axle. It seems doable if I take care

70sSanO

You can use a quick release with a claw type derailleur mount, but it should be an internal cam, old Campy, Shimano, Suntour style. I say this because I don’t know if the current skewer will be long enough with a longer axle. I would mount the current wheel with the short axle and see if the skewer will have enough threads to work.

If it doesn’t work, you’ll need to decide if you want to go with a longer quick release axle and quick release, or a nutted axle. If you go to a nutted axle it probably needs to be 10mm and not the typical 3/8”.

John

Gillparis

I can put the wheel on with the existing skewer if I squeeze the rear dropouts together to 135mm. I am not sure if this is a good idea - the skewer is only thin and I do not know if it should be under this sort of tension. With the normal width it is not long enough.

I will have a look at options for axles as well. Thank you!

70sSanO

Now I understand that the 142mm is between the dropouts. For a 20 year old mountain bike, this is an odd spacing.

As purely a guess, if the bicycle frame is steel, it is possible that someone decided to use a wider tandem wheel/hub on the rear and spread the dropouts to fit. If it is steel, you can bend it back to 135mm. If it is aluminum you are stuck with the 142mm.

But, every thing is relative to other components. If the previous rear wheel was a wider hub tandem wheel, it is possible that the crank is further out for a better chainline. In a hut shell, chainline is basically centering the chain on the cassette. For the “same speed cassette”, wider dropouts move it out and narrower move it in.

My advice is to put the new wheel in the dropouts and see where the chain lines up from middle of the crank to the middle of the freehub body. If it lines up, you could bend a”steel” frame back to 135mm. If it is aluminum, you could get a longer axle and add equal spacers on each side. Provided the wheel is centered.

If the chainline is off, “farther” from the spokes, it poses more issues including re-dishing the wheel.

John

Gillparis

Thank you. I checked and to me the chain looked good with the dropouts currently squeezed in to 135mm. The wheel and brakes all sit properly without needing adjusting. The frame is steel so I could bend them back in. Wouldn't I still need a longer axle anyway to reach the outside of the derailleur claw?

Sorry for all the questions!
Gill

70sSanO

Yes, you will need a longer axle to extend the claw derailleur width, while leaving enough clearance to be able to close the quick release against the dropout/claw and not bottom out on the axle.

It is important that there are enough threads screwed into the quick release skewer nut/cap.

John