4? All from glass in the tread on the rear. Standard Brompton rather than Marathons. Should probably spend more time pulling out the shards tbh but cba.
the amount of time wasted changing a Brompton rear tyre once will negate all the savings made in rolling resistance between that and a standard tyre...
How many have you had?
In two years of ownership I never had one, Paddington to Holborn 2x per day, with the marathons.
time for a new tyre?