Hi everyone, hopefully this will be of help to some.
For those that have been there, you will of course already know, Tehran in Iran, is a huge city and almost all shops are categorised into districts, so you need to go to a specific district area for certian types of items.
Well, having spent 18 days here now, some of them looking around at the bike shops that are common knowledge, today I hit upon some information that could have saved me many hours leg work and frustration.
In Tehran, there is a specific district for bicycle shops :-) . During my stay here I have visited maybe 6 bike shops that are known, and spent many hours walking the streets looking for others.
I'm sorry it is only in picture format (it's a photo of my notebook) but if you jump into a taxi and ask them to take you to GOMROK, you will find a complete street (I lost count after about 50 bike shops) dedicated solely to selling bikes. I was amazed that the information had not been posted on the web before, so felt obliged to pass on the info.
Picture of notebook, showing in farsi the place I asked (showed notebook) the taxi driver to take me.

Hope it is of some help.
OTW