Recently started biking to work on my old Ti MTB as I don't get enough riding time in otherwise !

I need some help turning it into a lightweight street-bike? How narrow a slick tyre is a good idea on standard MTB rims?

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.....but it still has to work!

1.0inch Slicks worked on my Mavic X517 rims.

Be carefull though... I had very bad experiences with Hutchinson Top Slick 1.0's. Both the light - and gold lined version. I had lots of punctures in them and they were not completely true... What good is a true rim when your tires have bends in them?!?

The Schwalbe Stelvio 1.0 Slick is a much better choice. Some bike-messenger colleagues of mine have used them without any problems. There's also a Continental 1.0 slick. I have not got any experience with that one, but given the reputation of Conti, if you can only get that one, it's a safe gamble.

If you go for light weight and an almost road bike - like feel, go for 1.0. If you want to seriously lower the risk of punctures and if you want some comfort, go for 1.2 or more. Stay away from Ritchey Tom Slicks - they suck when it's wet...

Thanks

....also thinking of cutting down my flat bars. Any experience on this?

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.....but it still has to work!

Yeah, I did lots of trial&error on bars...

I suppose the best way is to make a setup of your barends, brake levers and shifters WITHOUT cutting the bar. Just move everything inside, measure your grips and allow for space for them (Most of them are hard to move...).
Lots of people have a cm or perhaps 2 of room between the grip and brake lever - this aligns your first finger(s) much better to the curvature of most brake levers. If you're one of those people, allow for the extra space too.
This way you are able to test a setup and change things if it does not work for you. If you find a setup that works: Just cut your bars!

I did a lot of cycling in your hometown last weekend... I participated in the European Cycling Messengers Championships at the Eastway Cycle Circuit. Great stuff!! On sunday night we blocked Tower Bridge in both directions with a few hundred messengers... Have you heard anything about that?