What's the inside dimension of a fork or frame? Is there a standard?

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11/23/2019 10:50 AM

I ask cuz the 2 el cheapy bikes I have are different dimensions and the wheels are not compatible with each other. The front especially.

The back is close.... For some reason one of my frames is 4-1/4" and the other is 4-1/2" on the rear. And I can actually get the rim from the larger one into the smaller one, but not sure if it's that good for it The difference in front forks is a LOT different though. Which seems odd that it's different for front and back.....

One fork is 3-5/8" and one is 4-1/16".

On quality builds do they have a standard or what?

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Philippians 1:6 And I am sure of this, that he who began a good work in you will bring it to completion at the day of Christ Jesus. Insta: SilentNightSun

11/23/2019 11:30 AM

Do you mean distance between dropouts? It’s standard 100mm for forks and 110mm for frame. Sounds like either too much spacing on one, or not enough causing pinching. Mtb’s, road bikes etc are 135mm between dropouts on the frame.

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11/23/2019 1:32 PM

Yeah, the dropouts. Sorry. So, BMX forks and rear frame dimensions are usually the same?

Definitely not the case on the 2 cheap bikes I have.

I think the 2nd bike I have comes close to the dimensions you listed. Although I think the forks splayed out a little after taking off the front wheel. 100 mm = 3.9some odd inches and 110 = 4.33. That's close to what I was saying for the 2nd bike.

The first bike I got was meant for kids I think and probably had it's own dimensions for that type of a thing. Not as beefy.

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Philippians 1:6 And I am sure of this, that he who began a good work in you will bring it to completion at the day of Christ Jesus. Insta: SilentNightSun

11/23/2019 2:55 PM

actual kids bikes, like wal mart or target store bikes, are not actual bmx bikes. So i wouldn't count on expecting any standard.

What bikes are they and where did you get them?

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11/24/2019 4:00 PM

Got a Sunday Street sweeper frame new that was made wrong... Was 106mm between dropouts. Was a nightmare getting wheels in and caused hubs to fail quickly due to being pinched.

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11/24/2019 6:39 PM

Team who cares wrote:

Got a Sunday Street sweeper frame new that was made wrong... Was 106mm between dropouts. Was a nightmare getting wheels in and ...more

Any force from a pinched frame like that would be absolutely insignificant compared to the several tons you put on the hub when you tighten it to the frame.

Do you mean it'd damage/crack cones due to uneven loading?

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11/24/2019 6:51 PM

p1p1092 wrote:

Any force from a pinched frame like that would be absolutely insignificant compared to the several tons you put on the hub ...more

Those are my thoughts as well.. So what if the frame squeezed it a lil bit, that's nothing compared to any given wheel once properly tightened..

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11/24/2019 7:07 PM

Team who cares wrote:

Got a Sunday Street sweeper frame new that was made wrong... Was 106mm between dropouts. Was a nightmare getting wheels in and ...more

p1p1092 wrote:

Any force from a pinched frame like that would be absolutely insignificant compared to the several tons you put on the hub ...more

It put uneven pressure on bearings also made two clutch coasters make a grinding noise that only happened to each one in that frame. When put in multiple other frames with all the same parts including the chain the noise went away.
A colony wasp hub would ghost pedal constantly in that frame, not in any others.

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11/25/2019 8:31 AM
Edited Date/Time: 11/25/2019 8:32 AM

pnj wrote:

actual kids bikes, like wal mart or target store bikes, are not actual bmx bikes. So i wouldn't count on expecting any ...more

I realize this. I'm trying to learn to see if any of my cheap stuff will be compatible UNTIL I can afford a good one. Just trying to understand dimensions. It appears that the second bike I got has close to standard dimensions, but not the first. Which is fine, just want to know what I'm working with.

One came from the garbage and one came from FB marketplace for 20 bucks. It is what it is. I don't have any extra money right now and these were just something fun to start learning on. Right now I'm doing bunny hops and starting to learn other tricks on my 26" cruiser that I ride every day. And then I came across the free one and I'm fixing it up. And the second one I bought for the cranks and some parts. But could eventually build into a whole bike the way I want. It's a bit beefier frame.

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Philippians 1:6 And I am sure of this, that he who began a good work in you will bring it to completion at the day of Christ Jesus. Insta: SilentNightSun

11/26/2019 9:09 AM

Team who cares wrote:

Got a Sunday Street sweeper frame new that was made wrong... Was 106mm between dropouts. Was a nightmare getting wheels in and ...more

p1p1092 wrote:

Any force from a pinched frame like that would be absolutely insignificant compared to the several tons you put on the hub ...more

Team who cares wrote:

It put uneven pressure on bearings also made two clutch coasters make a grinding noise that only happened to each one in that ...more

This is good to know. I probably won't try to use the bigger rim on that frame.....

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Philippians 1:6 And I am sure of this, that he who began a good work in you will bring it to completion at the day of Christ Jesus. Insta: SilentNightSun